UC-NRLF 

III 

$B    EST    blM 

ia\L  COMMISSION  OF 

:    Cll.    FRED.    HARTT,    CHTEF. 


;APHICAL  SURVEYING, 


BE  YEAUX   CARPENTER,  C 

Geographer  to  the  Commission. 


FROM    VAN    NOSTKAND'S    MAGAZINE 


NEW   YORK: 

JSTOSTRAND,  PUBLISHER, 

|  MURRAY  AND  2T  WARREN  STREET. 

1O    K    o 
O     /    O   . 


VAN  NOSTRAND'S  SCIENCE  SERIES. 


VAN  NOSTRAND^UCIENCE  SERIES. 

No.  17.— WATER  AND  WATER  SUPPLY,  By 
PROF.  W.  H.  CORFIELD,  M.  A.,  of  the 
University  College,  London. 

No.  18.— SEWERAGE  AND  SEWAGE  UTILI- 
ZATION. By  PROF.  W.  H.  CORFIELD, 
M.  A.,  of  the  University  College,  Lon- 
don. 

No.  19.— STRENGTH  OF  BEAMS  UNDER 
TRANSVERSE  LOADS.  By  PROF. 
W.  ALLEN,  Author  of  "  Theory  of 
Arches."  With  Illustrations. 

No.  20.— BRIDGE    AND  TUNNEL    CENTRES. 

By  JOHN  B.  MCMASTERS,  C.   E.     With 

Illustrations. 
No.  21.— SAFETY  VALVES.      By  RICHARD    H. 

BUEL,  C.  E.     With  Illustrations. 

No.  22.— HIGH  MASONRY  DAMS.  By  JOHN  B. 
MCMASTERS,  C.  E.  With  Illustrations. 

No.  23.— THE  FATIGUE  OF  METALS  UNDER 
REPEATED  STRAINS,  with  various 
Tables  of  Results  of  Experiments.  From 
the  German  of  PROF.  LUDWIG  SPANGEN- 
BERG.  With  a  Preface  by  S.  H.  SHREVE, 
A.  M.  With  Illustrations. 

No.  24.— A  PRACTICAL  TREATISE  ON  THE 
TEETH  OF  WHEELS,  with  the  Theo- 
ry of  the  Use  of  Robinson's  Odonto- 
graph.  By  S.  W.  ROBINSON,  Prof,  of 
Mecha.iiical  Engineering.  Illinois  In- 
dustrial University. 

No.  25.— THEORY  AND  CALCULATIONS  OF 
CONTINUOUS  BRIDGES.  By  MANS- 
FIELD MERRIMAN,  C.  E.  With  Illustra- 
tions. 

No.  26.— PRACTICAL  TREATISE  O^T  THE 
PROPERTIES  OF  CONTINUOUS 
BRIDGES.  By  CHARLES  BENDER,  C.  E . 

No.  27.— ON  BOILER  ^INCRUSTATION  AND 
CORROSION.  By  F.  J.  ROWAN. 


GEOLOGICAL  COMMISSION  OF  BRAZIL, 

PROFESSOR   CH.    FRED.    HARTT,   CHIEF. 


GEOGRAPHICAL  SURVEYING, 

ITS  USES,  METHODS  Al  RESETS, 


BY 


FRANK  DE  YEAUX  CARPENTER,  C.E, 

Geographer  to  the  Commission. 


REPRINTED    FROM    VAN    NOSTHAND'S    MAGAZINE. 


NEW  YORK: 


D.  VAN  NOSTRAND,  PUBLISHER, 
23  MURRAY  AND  27  WARREN  STREET. 

1  8  78. 


Copyright ; 

18T8, 

By  D.  VAN  NOSTRAND. 
"' 


PREFACE. 


CHAKLES  FKEDERIC  HAKTT,  Professor 
of  Geology  in  the  Cornell  University, 
and  Chief  of  the  Geological  Commission 
of  Brazil,  died  on  the  eighteenth  of  March 
last,  in  Rio  de  Janeiro,  where  he  was 
engaged  in  preparing  the  reports  of  his 
Survey. 

His  death  and  the  dissolution  of  the 
Commission,  of  which  he  was  the  founder 
and  director,  have  prevented  the  realiza- 
tion in  Brazil  of  the  plan  of  surveying 
proposed  in  the  accompanying  pages. 

F.  D.  Y.  C. 

NEW  YORK,  July,  1878. 


GEOGRAPHICAL  SURVEYING. 


IN  this  paper  I  shall  present  a  scheme 
for  the  organization,  the  gradual  develop- 
ment, and  the  prosecution  of  a  geographi- 
cal survey  in  connection  with  the 
Geological  Commission,  which,  in  the 
efficiency  of  its  results,  will  satisfy  not 
only  the  present  demands  but  also  the 
future  needs  of  the  Empire  of  Brazil  for 
very  many  years  to  come.  In  the  rapidi- 
ty of  its  progress,  this  survey  will  be 
especially  adapted  to  a  country  of  so 
vast  an  area  and  comparatively  sparse 
population,  and  as  an  adjunct  to  the 
above  Commission,  and  in  great  part 
carried  on  by  the  members  of  the  same, 
without  interfering  with  the  ends  of 
that  body,  it  can  be  maintained  at  an 
expense  so  moderate  as  to  be  in  con- 
formity with  the  present  desire  for  econ- 


6 


omy   and    retrenchment    in    the   public 
service. 

THE  PROPOSED  PLAN  OF  SURVEY. 

The  immense  empire  of  Brazil  is  yet 
without  reliable  geographical  maps. 
These  are  necessary  to  the  national  wel- 
fare. The  question  arises  as  to  what 
kind  of  maps  will  be  sufficient  to  satisfy 
the  imperative  needs  of  the  country  and 
of  science.  The  plan  of  survey  which  I 
shall  advocate  is  a  mean  between  that 
system  which  takes  cognizance  of  every 
house  in  a  village  and  every  little  undula- 
tion in  the  landscape,  and  that  want  of 
system  in  which  are  represented  whole 
mountain-chains  that  do  not  exist,  or 
actual  topographical  features  are  delin- 
eated with  gross  inattention  to  accuracy. 
It  is  a  judicious  mean  between  the  slow 
and  laborious  processes  used,  for  in- 
stance, in  the  Ordnance  Survey  of  Great 
Britain,  and  the  sketchy  and  unreliable 
information  gained  by  the  early  ex- 
plorers of  the  New  World,  from  whose 
results  our  first  maps  were  compiled. 


These  last  are  scarcely  more  graphic  and 
complete  than  our  present  maps  of  the 
moon,  and  in  fact,  speaking  broadly, 
they  are  not  so  accurate  as  the  latter, 
which  are,  in  great  part,  photographs  of 
the  surface  which  they  represent.  With 
these  mere  hints  of  the  geography  of  its 
country  a  people  should  not  feel  obliged 
to  rest  satisfied  until  it  can  sustain  a 
minutely  topographical  survey. 

AN    EVOLUTION    IN    CARTOGRAPHY. 

The  demand  for  maps  depends  upon 
the  population  and  civilization  of  a 
country.  In  the  beginning  a  rough 
sketch  will  answer  the  purposes  of  the 
pioneer.  As  the  region  becomes  inhab- 
ited better  maps  are  wanted,  and  finally 
the  people  require  the  nearest  possible 
approach  to  absolute  accuracy  in  the  de- 
lineation of  topographical  features.  Map- 
making  in  every  country  must  follow  a 
regular  evolution  from  the  incomplete  to 
the  complete. 

Reviewing  the  origin  and  growth  of 
the  cartography  of  a  country,  we  see  how 
faulty  it  is  liable  to  be.  The  first  ex- 


plorer  is  the  first  contributor  to  the 
geography  of  a  region.  By  way  of  il- 
lustration, let  us  follow  one  of  these 
pioneers  as  he  traverses  Brazil  from 
South  to  North.  Following  up  a  branch 
of  the  River  Plate,  he  records  the  ap- 
proximate directions  and  distances  of  his 
journey,  which  he  obtains,  perhaps  by 
the  use  of  unreliable  pocket  instruments, 
perhaps  by  an  occasional  glance  at  the 
sun  and  his  watch,  or,  more  probably, 
by  estimating  at  night  the  latitude  and 
departure  which  he  has  made  during  the 
day.  At  a  certain  period  of  his  march 
he  finds  a  river  entering  from  an  easterly 
direction,  whose  volume  he  measures 
with  a  glance  of  the  eye.  Farther  on, 
he  encounters  a  tribe  of  Indians,  whose 
village  is  situated  upon  the  west  bank  of 
the  river;  he  counts  their  houses,  and 
makes  the  number  of  these  a  key  to  the 
extent  of  the  population.  At  the  fol- 
lowing night  he  camps  at  the  foot  of  a 
cataract.  Impressed  by  its  grandeur,  and 
also  by  a  kind  of  optimism,  common  to 
early  explorers,  and  which  will  not  allow 


him  to  underrate  any  of  the  glories 
which  he  sees,  he  estimates  its  height  to 
be  at  least  twenty  meters,  when  in  reality 
it  is  but  ten. 

At  a  certain  point  whose  latitude  and 
longitude  he  determines  in  a  rude  and 
hasty  way  with  the  sextant  which  he 
carries,  he  leaves  the  main  stream  and 
follows  a  tributary  to  its  head  in  the 
highlands,  where  he  crosses  the  divide  be- 
tween the  great  Parana — Paraguay  basin 
and  that  of  the  Amazon.  Upon  the 
summit  of  the  plateau  he  te'sts  his  alti- 
tude above  the  sea  by  noticing  the  tem- 
perature of  boiling  water,  or  by  reading 
the  indication  of  his  single  aneroid,  un- 
reliable methods  which  have  been  known 
to  give  results  even  a  thousand  meters 
wide  of  the  truth.*  Continuing  down 

*  Gibbon's  observations  at  the  head  of  the  Amazon, 
both  the  mercurial  and  thenno-barometer  being  used, 
show  a  discrepancy  between  the  two  which  is  equivalent 
to  300  meters  of  altitude.  The  height  of  Mount  Hood,  in 
Oregon,  as  given  by  one  authority,  who  determined  it  by 
the  boiling  point  of  water,  is  almost  2,000  meters  greater 
than  that  indicated  by  the  cistern  barometer  and  by  tri- 
angnlation.  In  the  writer's  own  experience  he  has  en- 
countered an  aneroid  record,  upon  one  of  the  peaks  of 


10 

the  Araguaya,  he  observes  the  trend  of  the 
mountain-range  along  his  route,  and,  de- 
scending the  Tocantins,  he  makes,  a  simi- 
lar survey  extending  to  Para. 

We  do  not  disparage  the  work  of  this 
man.  Under  the  circumstances  of  hard- 
ship and  peril  by  which  he  is  surrounded 
he  does  all  that  is  possible,  and  his  re- 
port is  really  of  great  value  until  some 
more  reliable  exploration  can  be  made; 
still,  for  all  of  that,  it  is  none  the  less  in- 
correct and  incomplete. 

It  is  from  such  sources  as  this  that  the 
material  for  our  first  maps  is  drawn.  In 
later  revisions  there  may  be  introduced 
the  results  of  desultory  explorations  of 
mines,  railway  routes  and  navigable 
waters,  as  well  as  the  meagre  topograph- 
ical data  acquired  by  the  land  surveyor 

the  Sierra  Nevada  Mountains  of  the  United  States,  which 
made  the  height  of  this  mountain  to  be  3,000  feet  above 
its  true  altitude.  It  is  a  noteworthy  fact  that  these  pre- 
liminary determinations,  made  with  the  above  faulty 
methods,  resemble  the  estimates  of  the  early  explorers, 
inasmuch  as  they  almost  invariably  give  exaggerated  alti- 
tudes ;  perhaps  the  opinions  and  imagination  of  the  ob- 
server are  allowed  to  form,  in  some  unaccountable  way, 
a  factor  in  these  results. 


11 


in  running  boundary  lines  of  private 
estates,  but  still,  taken  at  its  best,  a  map 
constructed  in  this  way  falls  far  short  of 
its  purpose  as  a  picture  of  the  conforma- 
tion of  the  earth's  surface,  or  as  a  guide  to 
the  traveler,  the  geologist,  or  to  the  capi- 
talist who  wishes  to  invest  his  money  in 
the  development  and  internal  improve- 
ment of  his  country. 

FAULTS  IN  EXISTING  MAPS. 

In  his  compilation  of  the  scattered  in- 
formation at  his  disposal  the  cartog- 
rapher finds  that  a  certain  district  of 
country  has  never  been  entered  by  the 
engineer.  He  knows,  however,  that  two 
rivers  rise  somewhere  in  this  terra  in- 
cognita, and  he  feels  it  safe  to  predicate 
a  divide  between  them.  He  also  thinks 
it  safe  to  presume  that  this  divide  is  a 
range  of  mountains,  of  greater  or  less 
height,  and,  in  his  desire  to  give  an  ap- 
pearance of  finish  to  his  chart,  he  does 
not  scruple  to  insert  at  this  place  an 
ideal  mountain  system,  and  represent 
it  as  drained  by  the  upper  tributaries  of 


12 

the  two  rivers,  concerning|whose  head- 
waters in  reality  nothing  is  known. 
These  physical  features  soon  come  to  be 
reproduced,  with  more  or  less  variation, 
in  other  maps,  and  in  this  manner  errors 
are  grounded  in  the  national  geography, 
from  which  they  can  only  be  eliminated 
by  a  systematic  geographical  survey. 
Like  national  myths  they  stubbornly 
refuse  to  give  way  until  eradicated  by 
true  scientific  research. 

Supposing,  on  the  other  hand,  that 
the  compiler,  accepting  the  report  of  the 
explorer,  who  claims  to  have  discovered 
a  range  of  mountains  between  the  Rio 
Parana  and  the  Rio  Araguaya,  wishes  to 
represent  them  upon  the  map.  He  has 
no  mathematical  data  to  insure  their 
position,  and  no  sketches  or  other  in- 
formation from  which  to  draw  their  in- 
tricate topographical  features,  and  so  he 
evolves  from  his  imagination  an  utterly 
impossible  chain  of  mountains,  out  of 
place,  artificial,  conventional,  and  even 
mechanical  in  their  regularity.  These 
he  depicts  in  that  stereotyped  form  of 


13 

delineation,  which  is  known  in  the 
modern  geographical  draughting-room 
as  the  "  caterpillar  "  formation. 

THE  RELATIONS  OF  GEOGRAPHY  TO  GEO- 
LOGY. 

Upon  such  an  unfaithful  map  as  this 
it  is  impossible  to  faithfully  represent 
the  geology  of  a  country.  If  the  geolo- 
gist attempts  to  lay  down  his  conclusions 
upon  a  sheet  of  this  kind,  its'  errors  will 
continually  clash  with  his  truths.  The 
configuration  of  the  land,  as  it  appears 
upon  this  erroneous  drawing,  might  in- 
dicate that  it  belonged  to  a  certain  geo- 
logical age,  and  that,  in  fact,  it  could 
not  be  referred  to  any  other;  the  geolo- 
gist, visiting  and  studying  the  country 
itself,  finds  that  it  is  of  a  later  and 
entirely  different  period.  But  if  he 
paints  it  as  it  really  is  he  publishes  a 
glaring  anachronism  to  the  world,  for 
the  color  which  represents  the  rock  of 
one  geological  epoch  overlies,  upon  the 
map,  the  physical  features  which  are 
peculiar  to  another  age.  As  in  the 


14 

artistic  and  true  delineation  of  tbe 
human  figure  every  feature  must  be  the 
exponent  of  anatomical  structure,  so  in 
topography,  every  representation  of 
topography  must  be  true  to  geological 
structure.  Ranges  of  mountains  mean 
disturbance  or  great  erosion  of  certain 
strata,  and  each  has  its  own  characteris- 
tic features  as  sharply  defined  as  those 
of  an  animal.  This  should  be  thoroughly 
understood,  and  those  immense  lines  of 
sierras  which  are  supposed  to  separate 
certain  river  basins,  or  are  delineated  in 
the  very  heart  of  regions  of  which  we 
have  no  knowledge  whatever,  should  be 
erased  from  the  national  maps  until 
these  districts  can  be  explored.  In  the 
course  of  his  travels  the  geologist  may 
find  some  physical  feature  of  great  im- 
portance, which  he  wishes  to  portray, 
in  area  and  position,  upon  his  chart,  but 
the  best  maps  at  his  disposal  represent  a 
topography  utterly  at  variance  with 
geological  structure,  perhaps  a  sharp 
ridge  of  mountains  where  there  should 
be  a  plain,  and  so  they  are  of  no  use  to 


15 

him.  Or  he  may  find  himself  obliged  to 
color  the  top  of  a  mountain  peak  with 
the  tint  conventional  to  the  bed  of  a 
lake,  and  in  this  manner  science  is  made 
ridiculous. 

To  take  an  illustration  nearer  home, 
suppose  that  the  group  of  mountains  that 
abut  into  the  sea  in  the  vicinity  of  Rio 
de  Janeiro  have  intervening  valleys  filled 
with  alluvium,  which  is  really  the  truth. 
Suppose  that  the  limits  of  these  mount- 
ains have  never  been  accurately  determ- 
ined, which  is  also  true.  In  this  case,  it 
is  easy  to  be  seen  that  if  the  geologist 
lays  down  upon  the  map  the  alluvial 
deposits  in  their  true  extent,  they  will 
here  and  there  encroach  upon  and  over- 
lap the  rugged  masses  of  gneiss,  and  in 
places  will  extend  far  up  the  steep  preci- 
pices of  the  mountain  side.  To  avoid 
this  absurdity  the  geologist  is  forced  to 
be  as  inaccurate  as  those  who  have  gone 
before  him,  and,  in  general,  every  error 
in  the  geographical  map  must  be  con- 
tinued and  apparently  sanctioned  in  the 
geological  chart  that  is  based  thereon. 


16 

It  becomes  therefore  absolutely  neces- 
sary that  the  work  of  the  geologist 
should  be  preceded  by  and  based  upon 
that  of  the  geographer,  and  that  he 
should  work  in  conjunction  with  the  lat- 
ter. In  the  exploration  of  a  new  coun- 
try the  geological  party  should  make  its 
own  topography  ;  and  in  the  United 
States  of  North  America,  where  the  ex- 
periment has  been  most  efficiently  tried, 
this  is  always  the  case. 

A  good  geographical  map  would  give, 
with  sufficient  completeness,  all  the  lead- 
ing topographical  features  of  the  region 
explored,  delineating  with  especial  care 
those  peculiarities  of  structure  which  are 
the  keys  to  the  different  formations.  It 
would  display  the  shape  and  position  of 
bodies  of  water,  and  show  how  the  di- 
rection of  a  stream  is  changed  and  de- 
termined by  the  accidents  of  a  broken 
and  displaced  stratification,  and  by  other 
circumstances  of  its  boundaries.  If  re- 
strained by  canon  walls  its  route  would 
be  angular;  down  a  steep  gradient  it 
would  be  direct;  and  in  the  level  allu- 


17 

vium  near  the  sea  its  track  would  be 
tortuous  and  broken  into  bayous.  This 
map  would  distinguish  between  the 
rounded  slopes  of  a  synclinal  valley  and 
the  abrupt  sides  and  angular  cross  sec- 
tion of  an  anticlinal  cleft;  and  between 
the  sharp  edges  of  the  volcanic  rock  and 
the  eroded  angles  of  the  sand-stone.  If 
there  was  exposed  a  great  "  fault "  in  the 
stratification,  it  would  show  it  at  a 
glance,  with  its  precipitous  bluff  of  ex- 
posed strata  on  one  side,  and,  on  the 
other,  its  gentle  declivity  of  tilted  sur- 
face rock.  And,  drawn  in  contour  lines, 
it  would  reveal,  not  only  the  heights  of 
peaks  and  passes  and  other  vertical  dis- 
tances from  plane  to  plane,  but  also  the 
various  orographic  forms,  each  of  which 
is  full  of  meaning  to  the  geologist. 

ECONOMICAL      USES     OF      THE      PROPOSED 
MAPS. 

Aside  from  being  quite  indispensable 
to  a  scientific  commission,  in  the  various 
ways  that  have  been  mentioned,  these 
maps  can  be  made  a  graphic  supplement 


18 

to  their  report  in  numerous  other  par- 
ticulars, and  can  be  made  to  embody  the 
stores  of  practical  information  which 
they  gather  incidentally  to  their  regular 
work.  Upon  it  they  can  display  the 
valleys  of  arable  land  and  the  plains 
adapted  to  grazing.  The  forests  of  tim- 
ber can  be  laid  down,  and,  from  this 
drawing,  their  areas  and  values  can  be 
closely  estimated.  Advantageous  sites 
for  colonies  can  be  noted  here.  The 
superficial  contents  of  coal-beds  and  ore- 
deposits  are  given,  and  not  only  does  a 
geological  chart  reveal  where  the 
precious  and  useful  minerals  are,  or  may 
be  found,  but  it  also  furnishes  that  nega- 
tive information,  equally  valuable  to  the 
miner,  which  defines  to  him  the  larger 
districts  in  which  it  is  impossible  for 
them  to  exist,  and  in  which,  consequent- 
ly, it  is  a  waste  of  effort  to  search  for 
them;  it  is  here  that  the  science  of 
palaeontology  is  especially  useful.  If 
any  portion  of  the  country  lies  at  a  great 
elevation,  the  altitude  limits  of  the  vari- 
ous forms  of  vegetable  growth  may  be 


19 

traced,  and  also  the  limits  of  the  possible 
culture  of  grain,  coffee,  cotton,  and  the 
other  principal  products.  In  this  man- 
ner the  map  is  made  a  general  statistical 
report  upon  the  value  of  the  national 
domain. 

The  economical  ends  served  by  a  work 
of  this  nature  in  the  development  and 
settlement  of  a  new  country,  cannot  be 
too  highly  esteemed.  Every  stream  of 
importance  is  surveyed,  in  all  except 
those  minor  branches  whose  courses  can 
be  traced  in  from  the  adjacent  mountain 
stations.  The  frequent  tests  for  altitude 
along  its  banks  determine  the  rapidity 
of  its  descent,  the  amount  of  water- 
power  which  it  represents,  and  its  value 
as  a  motor  for  machinery,  and  as  an 
agent  in  hydraulic  mining  and  diamond- 
washing.  This  profile  of  the  bottom  of 
the  valley  also  decides  the  feasibility  of 
railways  or  other  lines  of  communication 
by  this  route,  while  the  sketches  of  the 
adjacent  hills  show  what  room  there  is 
for  such  a  road,  and,  in  connection  with 
this,  the  geologist's  report  will  give  a 


20 

general  idea  of  the  rock  or  other  ma- 
terial with  which  the  engineer  will  have 
to  contend  and  work.  In  the  survey  of 
a  range  of  mountains  careful  readings 
for  altitude  are  made,  not  only  on  the 
summits  of  the  peaks,  but  also  at  the 
passes,  or  low  depressions  in  the  divide, 
while  the  slope  of  the  descent  from  the 
summit  to  the  valley  will  be  delineated 
in  contour  lines,  drawn  at  such  vertical 
distances  as  circumstances  may  require. 
It  must  be  admitted  that  these  contours 
will  only  approximate  to  their  true 
places,  yet  their  number  will  be  correct, 
and  their  positions  will  be  such  that  they 
will  give  with  sufficient  certainty  the 
various  gradients  that  occur  in  the  as- 
cent, so  that,  by  counting  the  meters  of 
rise  for  every  kilometer  of  horizontal  ad- 
vance, as  shown  by  the  scale  of  the  map, 
the  engineer  or  capitalist,  in  his  distant 
office,  with  this  sheet  before  him,  can 
form  a  very  satisfactory  idea  of  the 
practicability  of  a  proposed  railway,  and 
can  select  the  most  advantageous  route 
for  the  preliminary  survey. 


21 

The  meteorological  data  accumulated 
in  the  process  of  this  work  are  valuable, 
not  only  in  the  determination  of  the  ver- 
tical elements  of  the  survey,  but  also  as 
an  illustration  of  the  general  laws  of 
drought  and  excessive  rainfall.  At  in- 
tervals throughout  the  country,  the  de- 
clination of  the  compass  needle  will  be 
observed,  and  will  be  published  for  the 
guidance  of  land  surveyors  who  may  not 
be  proficient  in  astronomical  observation. 
The  positions  and  supra-marine  eleva- 
tions of  all  villages,  important  fazendas, 
medicinal  and  thermal  springs,  ancient 
ruins  or  other  discoveries  in  archaeology, 
supplies  of  water  in  a  dry  country,  or  of 
pasture  in  a  barren  district,  and  all  other 
places  of  interest  to  the  traveler,  will 
be  determined.  The  roads  and  trails 
already  in  existence  will  be  surveyed 
and  mapped,  while  a  leading  object  of 
this  enterprise  will  be  to  find  shorter  and 
easier  lines  of  travel.  The  explorer  who 
opens  a  new  pass  through  the  mountains 
is  a  far  greater  benefactor  to  mankind 
than  he  who  discovers  and  names  a  con- 
spicuous peak. 


22 

Many  of  the  national  surveys  of 
Europe  were  founded  on  military 
necessity,  that  is,  the  necessity  of  having 
correct  information  to  govern  the  move- 
ments of  armies  in  time  of  war  and  the 
incessant  transfer  of  troops  in  time  of 
peace.  In  some  of  these  countries  their 
early  maps  were  withheld  from  the 
citizen  whose  taxes  had  paid  for  their 
construction,  and  to  as  recent  a  date  as 
1857,  in  one  or  two  cases,  they  were 
kept  secret  for  use  in  some  contingent 
war.  This  argument  of  military  necessi- 
ty will  have  but  little  weight  in  Brazil, 
whose  rulers,  knowing  that  a  country 
strong  in  peace  will  also  be  strong  in 
war,  take  the  enlightened  and  advanced 
policy  of  encouraging  the  peaceful  pur- 
suits of  life,  as  the  surest  basis  of  nation- 
al strength.  Still  it  must  be  acknowl- 
edged that  these  maps  would  be  of 
excellent  service  in  the  administration 
of  the  affairs  of  distant  provinces,  in  the 
transportation  of  military  supplies,  and 
in  the  garrisoning  of  frontier  posts, 
although  the  country  is  to  be  congratu- 


23 

lated  that,  for  every  soldier  to  whom 
they  would  be  useful,  a  hundred  immi- 
grants would  be  benefited  by  them. 

THE  INTENTS  OF  THIS  ESSAY. 

While  entertaining  no  wish  to  make 
this  article  popular,  in  the  ordinary  sense 
of  the  word,  I  shall  seek  to  exclude  from 
it  all  formulas,  equations  for  computa- 
tion, and  other  material,  purely  mathe- 
matical, upon  which  the  surveyor  bases 
his  work,  and  as  far  as  possible  I  shall 
avoid  those  technical  terms  which  would 
be  embarrassing  to  the  reader  who  is  not 
an  engineer.  The  fundamental  princi- 
ples of  geographical  engineering  are  the 
same  all  the  world  over,  and  in  every 
mathematical  library  there  are  books  of 
reference  which  give  all  the  laws  and 
formulas  necessary  for  a  work  of  this 
kind.  Therefore,  nothing  would  be 
gained  by  their  repetition  here.  Spe- 
cialists in  geodesy,  astronomy,  and 
hypsometry  have  investigated  their  vari- 
ous branches,  have  published  their  re- 
sults, and  these,  in  their  purity,  are 


24 

applicable  to  any  quarter  of  the  globe. 
One,  for  instance,  has  applied  the  theory 
of  least  squares  to  geodetic  computa- 
tion; another  has  invented  the  zenith 
telescope  for  latitude  observations;  and 
a  third  has  traced  the  horary  curve  in 
the  barometric  record.  All  of  these  dis- 
coveries fall  within  the  comprehensive 
department  of  the  geographer,  who 
supplements  these  studies  by  utilizing 
their  results  in  his  labors  in  the  Held 
and  office;  or,  if  he  is  about  to  write  a 
brief  exposition  of  the  subject  of  geo- 
graphical surveying,  it  is  his  business  to 
describe,  in  a  straightforward  manner, 
the  way  in  which  practical  application 
of  these  truths  is  made. 

This  paper  will  be,  in  general,  a 
description  of  the  most  approved  meth- 
ods, the  economical  devices,  and  the 
practical  results  of  a  successful  geo- 
graphical survey,  working  in  obedience 
to  the  directions  of  the  chief  of  the 
commission  to  which  it  is  attached,  and 
covering  such  areas  as  may  be  designated 
by  him  as  most  worthy  of  geological 


25 

and  geographical  delineation.  From 
time  to  time,  as  occasion  may  offer,  and 
especially  at  the  conclusion,  the  project 
will  be  adapted  to  the  Empire  of  Brazil, 
as  it  is  quite  impossible  to  propose  a 
plan  of  survey  which  will  be  applicable 
to  all  countries.  Although,  as  has  been 
stated  heretofore,  the  general  principles 
underlying  this  kind  of  work  are  the 
same  wherever  physical  laws  prevail, 
and  the  face  of  the  country  is  wrinkled 
with  mountains  and  valleys  and  furrowed 
with  the  river-bed  and  canon,  yet  there 
are  physical  conditions  peculiar  to  every 
land,  as  well  as  circumstances  of  area, 
population,  and  wealth,  which  require 
that  it  should  have  its  own  type  of  geo- 
graphical survey,  and  not  copy  too  ex- 
actly those  of  any  other  nation. 

THE  BEST  TYPE  OF  SURVEY  FOR  BRAZIL. 

Considering  the  circumstances  of  area, 
population,  and  wealth  it  is  evident  that 
the  national  surveys  of  Brazil  should  be 
"  geographical "  in  a  very  liberal  sense  of 
the  word;  that  is,  that  they  should  be 


26 

comprehensive  in  their  scope,  rapid  in 
their  execution,  and  sufficiently  accurate 
without  being  too  punctilious  and  too 
excessively  minute.  It  is  only  within 
the  present  generation  of  engineers,  and 
particularly  in  the  western  hemisphere, 
that  there  has  grown  up  an  important 
distinction  between  topographical  and 
geographical  surveying,  and  even  now  it 
is  hard  to  define  the  limit  between  them. 
The  latter  is  an  outgrowth  and  extension 
of  the  former  and  an  adaptation  of  it  to 
the  mapping  of  large  domains  at  the 
least  possible  expenditure  of  money  and 
time. 

DISTINCTION  BETWEEN    THE    GEOGRAPHER 
AND   TOPOGRAPHER. 

As  one  of  the  many  points  of  differ- 
ence between  the  geographer  and  the 
ordinary  topographer,  we  may  mention 
that  the  former,  in  his  travels  and  sur- 
veys, accommodates  himself  to  the  roads, 
trails,  or  other  open  and  easy  routes  that 
already  exist,  and  it  is  but  seldom  that 
he  finds  himself  obliged  to  make  a  path 


27 

for  his  survey  to  follow.  In  the  ascent 
of  some  mountains  it  may  be  necessary 
to  cut  a  road,  and  in  the  measurement  of 
the  base  line  for  his  triangulation  he  may 
have  to  prepare  the  ground  before  him, 
but  these  are  almost  the  only  instances. 
The  topographer,  however,  in  tracing  a 
contour  line  around  the  side  of  a  mount- 
ain, or  in  making  parallel  profile  sec- 
tions of  the  land,  is  not  allowed  to  devi- 
ate therefrom,  and  if  the  way  is  not 
clear,  he  must  wait,  perhaps  at  great  loss 
of  time,  until  his  assistants  have  removed 
the  brushwood,  or  whatever  other  obsta- 
cles may  intervene  ;  in  this  respect  he 
resembles  the  railway  engineer.  Again, 
in  the  selection  of  the  stations  for  his 
triangulation,  the  geographer  makes  the 
best  possible  use  of  the  mountains 
of  a  country  as  he  finds  them,  generally 
accepting  them  as  they  occur;  though 
their  arrangement,  it  may  be  confessed 
here,  is  not  always  in  such  well-condi- 
tioned triangles  as  he  would  desire.  The 
topographer,  on  the  contrary,  delays  his 
work  by  the  establishment  of  arbitrary 


28 

stations  where  natural  points  are  lacking, 
and  by  the  erection  of  artificial  signals 
on  those  mountain  tops  which  the  former 
observes  without  such  aid. 

In  the  end  it  will  be  found  that  the 
topographer's  notes  are  so  numerous  and 
in  such  detail  that  it  may  require  several 
centimetres  of  map  to  represent  one  kilo- 
metre of  the  earth's  surface;  while  to 
the  geographer,  who  is  satisfied  with  the 
general  shape  of  a  mountain- spur,  the 
approximate  width  of  a  valley,  and  the 
more  important  bends  of  a  stream,  a 
scale  of  one  centimetre  to  several  kilo- 
metres may  be  sufficiently  large  for  the 
portrayal  of  the  earth  as  he  finds  it.  But 
it  will  also  be  observed,  by  an  economi- 
cal government,  that  while  the  topog- 
rapher consumes  several  years  in  the 
survey  of  a  thousand  square  kilometres, 
the  geographer  will  obtain  a  very  satis- 
factory knowledge  of  thousands  of 
kilometres  in  one  year.  And,  in  general, 
the  superior  accuracy,  or  rather  detail,  of 
the  former,  is  purchased  at  an  expendi- 
ture of  time  and  money  so  great  that 


29 

only  the  older  and  wealthier  nations 
can  afford  the  investment;  while  I  hope 
to  demonstrate  that  the  geographer's  re- 
sults are  sufficiently  complete  for  the 
needs  of  Brazil. 

THE  GEOGRAPHER'S  PROFESSION. 

The  geographer's  work  is  a  peculiar 
and  difficult  one,  and  one  for  which  his 
ideas  must  become  enlarged  by  a  special 
training.  This  is  a  branch  of  our  pro- 
fession for  which  no  training-school  pre- 
pares its  student  and  no  text-book  yet 
published  can  instruct  him.  This  is  a 
field  in  which  the  experienced  topog- 
raphical engineer,  fresh  from  his  labors 
on  park  and  landscape,  or  on  the  detailed 
surveys  of  thickly-populated  Europe, 
finds  himself  unhandy  and  incompetent, 
for  much  of  the  experience  and  tradition 
that  he  brings  with  him  is  an  incubus 
to  retard  him.  To  become  efficient  in 
this  new  service  he  must  forget  much  of 
the  rule  and  routine  that  he  has  learned, 
and  accustom  himself  to  taking  broad 
and  bird's-eye  views  of  the  country. 


30 

Strange  as  it  may  sound,  he  must 
make  it  a  matter  of  duty  and  pride  to 
overlook  and  neglect  much  that  is  near 
at  hand,  and  remember  that,  although  a 
mole-hill  at  a  distance  of  a  few  feet  sub- 
tends a  greater  visual  angle  than  a 
mountain  as  many  miles  away,  yet  it  is 
the  mountain,  and  not  the  mole-hill,  that 
deserves  delineation  upon  his  map. 
Hitherto  he  has  been  local  and  narrow  in 
his  range;  he  must  now  become  geodetic, 
else  he  will  accumulate  a  mass  of  minu- 
tiae, whose  representation  would  be  in- 
finitesimal on  a  map  of  the  proposed 
scale,  and  which  is  hence  but  an  incum- 
brance  to  his  books,  and  even  worse  than 
cumbersome,  inasmuch  as  its  presence 
excludes  other  and  more  valuable  data. 
In  short,  the  topographer  considers  the 
earth  minutely,  and  with  a  microcosmic 
view,  but  the  geographer  is  a  man  of  no 
such  narrow  horizon,  and  trains  himself 
to  look  upon  it  as  a  macrocosm,  or  great 
world. 


31 


THE    INSTRUMENTS    USED. 

Of  scarcely  secondary  importance  to 
the  men  of  a  geographical  corps,  are  the 
instruments  with  which  they  shall  work. 
The  tools  which  have  been  devised  for  the 
ordinary  surveys  of  land  and  landscape 
must  be  left  at  home  with  the  slow  and 
tedious  methods  from  which  they  cannot 
be  divorced.  In  a  work  of  geographical 
extent  the  spirit-level,  chain,  and  tally- 
pins  are  out  of  place,  and  whosoever, 
making  accuracy  his  plea,  attempts  to  in- 
troduce them  there,  will  find  his  own 
ends  defeated  by  them.  Once  upon  a 
time,  for  instance,  an  engineer  was  in- 
trusted with  the  survey  of  a  large  tract 
of  new  country.  A  certain  sum  of 
money  and  a  limited  period  of  time  were 
given  to  him,  a  stated  area  of  territory 
was  assigned  to  him,  and  in  return  the 
authorities  expected  of  him  the  most  ac- 
curate and  impartially  complete  map 
that  his  means  would  allow. 

The  time  and  resources  granted  him 
would  permit  him  to  touch  the  country 
but  lightly  and  by  swift  marches,  but,  as 


32 

this  was  intended  to  be  only  a  reconnois- 
sance,  nothing  more  was  expected  of  him 
than  to  trace  the  conformation  of  the 
land  in  a  general  way.  He  was  an 
honest  and  conscientious  engineer,  and 
so  great  was  his  zeal  for  accuracy,  or 
nicety  rather,  that  he  was  scrupulous  to 
a  fault.  He  abused  the  maxim  which 
says  that  whatever  is  worth  doing  at  all 
is  worth  doing  well.  For  determining 
the  altitude  of  stations  along  the  route 
he  used  the  spirit-level,  and  their  inter- 
mediate distances  were  found  by  stadia 
measurements,  which  system,  though 
considered  incautiously  rapid  in  topogra- 
phy, is  too  laggardly  slow  for  the  or- 
dinary purposes  of  geography.  In  this 
manner  he  crossed  his  territory  with  a 
few  lines  of  march  whose  profiles  were 
as  trustworthy  as  those  of  a  railway  sur- 
vey, and  far  more  accurate  than  the  pub- 
lic interest  demanded,  while  between 
them  there  were  large  areas  untouched 
and  unseen,  and  of  these  the  public, 
whose  agent  he  was,  had  commissioned 
him  to  obtain  information.  The  failing 


33 

of  this  engineer  was  a  common  one;  he 
neglected  to  distribute  his  resources 
fairly  and  impartially,  and  while  half  of 
his  map  is  reliable  the  other  half  is  con- 
jectural. 

It  would  be  too  long  a  task  to  de- 
scribe in  detail  all  the  instruments  used 
in  geographical  work,  or  to  rehearse  all 
of  the  devices  employed  in  its  prosecu- 
tion; however,  the  most  necessary  and 
novel  features  will  be  noticed  here.  At 
the  basis  of  the  work  is  the  transit,  or 
theodolite,  which,  with  compass-needle 
attached,  is  the  engineer's  constant  com- 
panion, without  which  his  occupation  is 
gone,  no  matter  in  what  field  his  labor 
may  lie.  As  an  appurtenance  to  this, 
not  the  chain  nor  the  stadia,  but  the 
odometer  wheel,  has  become  the  recog- 
nized means  of  linear  mensuration  in  the 
survey  of  streams  and  the  determination 
of  those  distances  of  route  and  detour 
which  are  so  useful  in  filling  in  a  trian- 
gulation  chart.  Instead  of  the  level,  the 
cistern  barometer  gives  the  heights  of 
mountains,  mines,  passes,  camps,  vil- 


34 

lages,  and  other  important  positions, 
while  the  aneroid  barometer,  portable  as 
a  watch,  and  as  easily  read,  will  tell  the 
altitude  of  minor  points  and  give  with 
sufficient  closeness  the  data  from  which 
may  be  plotted  the  profile  of  the  odome- 
ter's itinerancy. 

THE     PERSONNEL     OF     A     GEOGRAPHICAL 
CORPS. 

These  are  the  three  classes  of  instru- 
ments that  are  indispensable;  the  purely 
geographical  party  required  to  use  them 
need  consist  of  but  three  men,  the  en- 
gineer, the  meteorologist,  and  the 
odometer  recorder.  To  this  corps  it 
may  be  deemed  advisable  to  add  a  fourth 
member  to  act  as  an  assistant  to  the  en- 
gineer, and,  by  personal  obervation  and 
experience  acquire  that  facility  in  the 
practice  of  his  profession  which  will  fit 
him,  in  the  course  of  a  brief  period  of 
training,  for  the  responsible  position 
above  him.  Such  a  person  should  al- 
ready have  the  theoretical  education  of 
an  engineer,  and  some  skill  in  drawing. 


35 

If  it  is  not  practicable  to  make  this  ad- 
dition to  the  corps,  it  is  well  to  choose 
as  an  odometer  recorder  one  who  pos- 
sesses the  acquirements  stated  above, 
and  to  consider  that  position,  whose 
appertaining  duties  are  light,  as  prepar- 
atory to  the  grade  of  engineer.  As  for 
the  meteorologist,  his  is  an  intricate 
science  which  cannot  be  studied  too 
thoroughly,  and  barometric  hypsometry 
should  be  regarded  as  a  profession  quite 
distinct  from  the  engineer's,  although 
necessarily  subordinate  to  it. 

The  various  duties  involved  in  the 
measurement  of  the  base-line,  at  the 
opening  of  the  season,  may  demand  the 
services  of  a  larger  body  of  men  than 
this,  but,  once  in  the  field,  any  addition 
to  the  above  number,  except  as  muleteers 
and  servants,  will  be  superfluous,  as  far 
as  the  geographical  work  is  concerned. 
One  surveyor  can  see  as  far  as  two,  and 
one  man  is  able  to  take  note  of  all  of  the 
country  visible  from  his  route  of  travel. 
No  axemen  are  needed,  for  if  there  is  a 
tree  in  the  way,  the  line  must  yield  to 


36 

the  tree;  the  resultant  error  will  be  trif- 
ling and  will  not  be  apparent  in  a  map 
which  represents  several  kilometres  of 
territory  on  one  centimetre  of  space. 
Neither  is  there  any  necessity  for  rod- 
men,  with  rods  of  two  targets  for  mi- 
crometer measurements  or  one  target  for 
levels,  who  would  retard  the  corps  by 
the  long  delays  consequent  upon  their 
transfer  from  the  stations  in  the  rear  to 
those  in  advance.  This  party  travels  as 
a  unit,  moving  as  fast  as  its  animals  can 
walk,  and  is  never  broken,  a  considera- 
tion which  is  of  value  in  a  country  of 
hostile  people. 

Of  course  the  scope  of  the  work  may 
require  the  service  of  a  great  number  of 
professional  men,  but  its  best  progress 
demands  that  they  should  be  divided 
into  corps  of  the  above  size,  which  shall 
work  in  concord  and  under  one  general 
liead.  This  director  will  assign  to  each 
party  its  territory  for  the  season,  and 
tupon  the  borders  of  these  areas,  the  va- 
rious engineers  will  make  rendezvous 
from  time  to  time,  as  circumstances  may 


37 

admit,  with  their  neighbors  of  the  ad- 
joining fields,  for  the  purpose  of 
reorganization,  exchange  and  issue  of 
material,  and  especially  for  the  compari- 
son of  sketches  and  geodetic  data,  so  as 
to  insure  the  proper  union  of  their  sev- 
eral schemes  of  triangulation.  In  order 
to  make  the  different  systems  of  trian- 
gles interlock  in  one  grand  plan,  the 
observer  will  frequently  be  obliged  to 
read  angles  to  stations  which  lie  in  an 
adjacent  district,  and  which  will  be  oc- 
cupied by  his  co-laborers  for  the  purpose 
of  reciprocal  observations.  It  is  there- 
fore necessary  that  they  should  meet  in 
occasional  conference  for  the  mutual 
identification  of  those  stations. 

THE  STATIONS  OF  SURVEY. 

Guided  by  these  thoughts,  let  us  sup- 
pose that  we  have  completed  our  organi- 
zation for  a  season  in  the  field,  and  that 
we  are  now  on  the  ground  ready  for 
work,  at  the  place  selected  as  the  initial 
point  of  the  survey.  As  with  all  surveys, 
this  one  will  be  executed  from  stations, 


38 

meaning  thereby  any  points  at  which  a 
tripod  is  planted  and  an  instrument  ad- 
justed, angles  are  read  and  sketches  may 
be  made.  Of  these  we  shall  occupy 
four  orders,  of  which,  in  importance,  and 
consequently  in  accuracy,  the  astronomi- 
cal is  first.  Then  comes  the  geodetic,  or 
triangulation  station;  the  topographical 
station,  so  designated  for  the  sake  of  con- 
venience; and,  finally,  the  odometric,  or 
route  station.  In  addition  to  the  ends 
which  they  are  especially  intended  to 
serve,  each  of  these  will  be  a  meteorologi- 
cal station  as  well.  These  five  classes, 
with  the  incidental  details  pertinent  to 
them,  will  now  be  considered  in  the 
order  named. 

THE  ASTRONOMICAL  STATION. 

Since  the  positions  determined  by  tri- 
angulation, or  other  system  of  survey  in 
which  terrestrial  objects  alone  are  con- 
sidered, are  only  relative  to  each  other 
and  to  the  first  station  occupied,  it  is 
evident  that  a  map  may  be  completed, 
which,  in  itself,  will  have  all  of  the  ex- 


39 

actness  of  perfect  truth,  but  whose  place 
on  a  projected  surface  of  the  globe  will 
still  be  uncertain.  A  map  of  a  conti- 
nent may  be  made,  and  this  may  be  of 
great  use  in  the  guidance  of  travelers 
across  the  continent,  and  for  the  local 
information  of  its  inhabitants,  but  still 
it  does  not  play  its  proper  part  in  the 
grand  plan  of  this  earth's  geography,  and 
define  the  situation  of  this  land  relative 
to  the  other  continents  of  the  earth, 
until  it  is  bound  into  place  by  the  meri- 
dians and  parallels,  which  are  the  warp 
and  woof  of  the  structure  of  geography. 
Therefore,  in  order  to  adjust  our  map, 
when  made,  into  its  true  place,  we  must 
have  the  absolute  determination  of  one 
or  more  of  its  positions. 

Now  there  is  but  one  way  of  finding 
the  absolute  position  of  an  object  on  the 
earth,  and  that  is  by  going  beyond  the 
earth,  consulting  the  stars,  and  ascer- 
taining its  place  relative  to  them.  Hav- 
ing two  triangulation  stations  thus 
located,  the  whole  chart  becomes  ad- 
justed to  its  place.  Or,  having  the  lati- 


40 

tude  and  longitude  of  our  initial  point 
and  the  astronomical  azimuth  of  a  side 
of  a  triangle  leading  from  this  origin,  the 
former  serves  to  pin  the  plot  to  the  pro- 
jected map,  and  the  latter  is  instrument- 
al in  orienting  it  into  the  area  to  which 
it  belongs. 

POSITION  OF  THE    ASTRONOMICAL  STATION. 

For  every  base-line  measured  and 
developed  there  should  be  an  astronomi- 
cal station  occupied,  and  as  a  matter  of 
convenience  and  co-operation  they  should 
be  in  the  same  vicinity,  although  it  is 
not  necessary  that  the  station  should  be 
directly  over  either  end  of  the  base. 
Indeed,  owing  to  great  exposure  to 
the  wind,  or  to  inconvenience  of  ap- 
proach, it  may  not  be  found  practicable 
to  locate  the  astronomical  station  at  any 
of  the  points  of  the  triangulation  system, 
or,  to  secure  proximity  to  the  telegraph, 
whose  office  may  be  hidden  in  the  heart 
of  a  town,  or  the  bottom  of  a  valley,  it 
may  be  so  secluded  as  to  be  quite  in- 
visible from  those  points. 


41 

If  so,  it  may  be  easily  connected  with 
them  by  running  a  careful  linear  survey 
from  the  astronomical  station  to  the 
nearest  geodetic  station.  If,  owing  to 
the  disadvantageous  nature  of  the 
ground,  or  other  obstacles  in  the  way,  it 
may  be  impossible  to  measure  the  dis- 
tance directly  between  these  two  points, 
the  engineer  can  connect  them  by  a 
broken  line,  reading  at  the  astronomical 
station  the  angle  between  the  meridian 
mark,  already  fixed  by  the  astronomer, 
and  the  direction  of  his  first  course,  and 
afterwards  referring  the  direction  of  each 
measured  section  of  his  traverse  to  that 
immediately  preceding.  From  these  re- 
sults he  calculates,  in  meters,  the  differ-  • 
ence  of  latitude  and  departure  between 
the  two  points,  and  then,  transforming 
the  meters  into  seconds  of  arc,  he  com- 
putes their  difference  of  latitude  and 
longitude. 

NUMBER  OF  ASTRONOMICAL  STATIONS. 

For  a  commission  of  moderate  size,  in- 
cluding one,  two,    or  three  engineering 


42 

corps,  the  triangular  development  of  one 
base  will  cover  as  much  territory  as  can 
be  surveyed  by  them  in  a  single  cam- 
paign, and  therefore  one  astronomical 
position  a  season  is  all  that  this  survey 
would  require  during  the  first  year  or 
two  of  its  organization.  A  series  of  ob- 
servations extending  through  a  couple  of 
weeks,  in  favorable  weather,  or  through 
a  month  at  the  farthest,  will  determine 
the  geographical  co-ordinates  of  our 
point  of  departure.  These  can  be  made 
by  the  astronomer  while  the  engineers 
are  measuring  the  base-line  and  develop- 
ing the  same,  the  director  is  perfecting 
his  arrangements,  and  the  purveyors  are 
preparing  and  distributing  the  supplies, 
instruments,  and  all  of  those  numerous 
articles  of  equipment  which  are  the  fur- 
niture of  a  scientific  field  season.  At 
the  same  time,  the  meteorologist,  by  a 
set  of  hourly  barometric  and  psychro- 
metric  readings  accumulates  data  whose 
digest  will  give  the  vertical  co-ordinate 
of  this  place  with  the  possible  error  of  a 
very  few  feet,  and  this  completes  the  de- 


43 


termination  of  its  position  with  reference 
to  a  system  of  co-ordinates  whose  origin 
is  at  the  level  of  the  sea  at  the  point 
where  the  first  meridian  crosses  the 
equator. 

For  so  short  an  annual  term  of  service 
it  might  not  be  advisable  to  keep  an  as- 
tronomer constantly  in  commission,  nor, 
at  present,  might  it  be  well  to  go  to  the 
expense  of  the  costly  and  elaborate  in- 
struments requisite  for  the  best  astro- 
nomical observation,  provided  that  the 
co-operation  of  the  Imperial  Observatory 
could  be  secured  and  an  astronomer 
could  be  detailed  from  there  for  that 
purpose.  In  addition  to  the  gratification 
to  be  derived  from  the  warranted  excel- 
lence of  the  results  which  would  be  fur- 
nished by  the  skilled  assistants  of  that 
institution,  this  cooperation  would  be  a 
matter  of  economy  to  the  Government? 
and  also,  what  is  especially  to  be  desired 
between  any  two  scientific  bodies,  a 
means  of  friendly  relation  and  inter- 
change of  information  which  would  cer- 
tainly prove  of  mutual  value. 


44 


ASTRONOMICAL   METHODS. 

For  the  determination  of  the  latitude 
of  our  point  of  outfit  the  zenith  tele- 
scope would  be  used;  while  the  longitude 
would  be  found  by  the  telegraphic  ex- 
change of  time  signals,  a  method  which 
has  lately  been  so  successfully  introduced 
by  the  Astronomical  Commission.  The 
present  wide-spread  extension  of  lines 
of  electric  telegraph  within  the  borders 
of  Brazil  is  especially  favorable  for  a 
survey  of  this  nature,  whose  longitudes 
would  be  based  upon  telegraphic  commu- 
nication with  the  national  observatory. 
The  lines  along  the  coast  afford  a  gen- 
eral connection  with  the  northern  and 
southern  provinces  of  the  Empire,  while, 
by  the  numerous  branches  which  accom- 
pany the  railways  into  the  interior,  points 
which  lie  far  to  the  inland  could  be  re- 
ferred to  the  meridian  of  Eio  de  Janeiro, 
which,  in  its  turn,  has  communication 
by  cable  with  the  observatories  of  Eu- 
rope. 

Thus  it  will  be  seen  that  the  engineer 
need  not  be  confined  to  any  unfavorable 


45 

locality  in  the  selection  of  the  ground 
for  his  base  line,  nor  need  the  chief  of 
the  commission  be  restricted  in  his  choice 
of  areas  to  be  surveyed.  From  the 
railways  either  constructed  or  contem- 
plated it  would  probably  be  possible  to 
reach  any  of  the  settled  portions  of 
Brazil  without  seriously  overtasking  the 
accuracy  of  the  triangulation,  and,  if  it 
were  required  to  carry  the  survey  still 
farther,  longitudes  determined  by  the 
method  of  moon-culminations  would  be 
sufficiently  exact  for  the  less  important 
regions  beyond. 

ORIGIN    OF    THE    TKIANGULATION. 

An  inland  survey,  based  upon  trigono- 
metrical methods,  progresses  most  suc- 
cessfully from  an  initial  source  concen- 
trically outwards.  The  most  fortunate 
location  for  the  initial  line  is  in  the  cen- 
ter of  some  broad  valley  or  intermontane 
plateau,  whose  level  expanse  offers  fair 
ground  for  the  measurement  of  the  base, 
and  whose  open  field  is  favorable  for  the 
gradual  and  symmetrical  development 


46 

of  the  same  until  it  shall  reach  the  lines 
of  the  remotest  triangles,  in  which  it  be- 
comes a  metrical  standard  for  finding 
their  length.  In  an  extensive  survey, 
lasting  for  years  and  covering  broad  ter- 
ritory, a  series  of  bases  are  indispensa- 
ble. These  act  as  checks  upon  each 
other,  and  the  net-works  of  triangles 
emanating  therefrom  are  dovetailed  into 
each  other,  and,  in  their  adjustment  to 
fit,  each  to  each,  what  little  error  they 
may  have  accumulated  is  reduced  to  a 
minimum. 

For  instance,  on  each  side  of  a  range 
of  mountains  there  is  an  open  basin.  In 
each  of  these  an  astronomical  station  is 
established  and  a  base  is  measured.  On 
the  comb  of  the  intervening  sierra,  one- 
hundred  miles  apart,  stand  two  pre-emi- 
nent mountain  peaks.  The  latitude  and 
longitude  of  each  of  these,  with  the 
distance  between  them,  is  determined 
from  the  two  origins  independently. 
They  check  each  other,  verifying,  in 
their  agreement,  the  accuracy  of  both 
systems,  or  showing  by  their  disagree- 


ment  that  there  is  an  error  somewhere^ 
and  the  long  line,  drawn  by  the  labor- 
saving  appliances  of  trigonometry, 
through  a  hundred  kilometres  of  aerial 
route,  a  thousand  meters  above  the  val- 
leys and  chasms  which  it  spans,  is  now 
ready  to  be  used  as  a  new  base  in  the 
primary  triangulation. 

It  may  be  difficult  to  find  a  favorable 
locality  for  the  source  of  a  triangulation 
immediately  upon  the  sea-shore,  as  there, 
unless  there  are  islands  in  the  adjacent 
ocean,  one  side  of  the  field  is  quite  open 
and  affords  no  stations  to  be  occupied. 
If  it  were  not  for  this  objection  it  would 
seem  best  to  measure  a  succession  of 
bases  along  the  coast  of  Brazil,  and 
thence  develop  them  westward.  A  tri- 
angulation is  always  most  accurate  in 
the  vicinity  of  its  origin,  and  as  it  be- 
comes more  and  more  remote  from  its 
initial  ground  it  becomes  less  reliable, 
owing  not  only  to  the  continued  multi- 
plication of  the  original  error  of  the 
base,  but  also  to  the  accumulation  of  in- 


48 

accuracy  and  mistake  *  from  other 
sources.  Now,  the  population  of  Brazil 
is  thickest  along  the  sea,  and  thence,  into 
the  interior,  at  least  in  many  provinces, 
it  gradually  thins  out.  The  importance 
of  the  country  and  the  necessity  of 
having  truthful  maps  correspond  to  the 
density  of  the  population.  Add  to  this 
the  fact  that  the  most  interesting  geology 
of  Brazil  is  on  the  sea-board,  and, 
furthermore,  the  important  considera- 
tion that  the  coast  of  a  country,  for  pur- 
poses of  navigation,  demands  a  more 
rigorous  geographical  determination  than 
the  interior,  and  it  will  be  seen  that  the 
triangulation  upon  which  this  delineation 
depends  should  not  originate  too  far 
away.  In  a  general  survey  of  Brazil, 
therefore,  the  first  series  of  astronomical 
stations  and  bases  should  be  established, 
if  not  upon  the  sea-shore  itself,  at  least 

*  There  is  an  important  difference  in  the  meanings  of 
the  terms  "mistake"  and  "inaccuracy."  If  a  man, 
carelessly  reading  a  vernier  whose  indication  is  38'  45", 
calls  it  39'  45",  he  is  guilty  of  a  mistake.  If  from  parallax 
or  some  defect  in  vision  or  judgment,  he  calls  it  38'  40", 
he  is  inaccurate.  Mistakes  are  due  to  want  of  care ;  in- 
accuracy, to  want  of  precision. 


49 

upon  the  first  plateaus  that  are  encount- 
ered between  the  mountains  of  the  in- 
land. 

POSITION    OF   THE    BASE-LINE. 

In  its  direction  and  position  the  base- 
line should  bear  judicious  relations  with 
certain  hills,  knolls,  corners  of  terraces, 
or  other  prominent  elevations  in  the  vi- 
cinity, which  may  be  selected  as  sites 
for  the  stations  to  be  occupied  in  its  de- 
velopment. The  plans  for  its  expansion, 
matured  before  its  position  is  selected, 
should  include  two  prominent  peaks  in 
the  horizon,  remote  from  the  origin  and 
from  each  other,  whose  distance  apart 
this  measured  length  will  be  instrumental 
in  determining.  The  ground  upon  which 
it  is  to  be  measured  should  be  as  smooth 
and  bare  as  possible.  It  should  be  free 
from  brush,  tall  grass,  or  other  vegeta- 
tion, and  also  from  hillocks  and  gulches, 
which  are  serious  impediments  to  a  work 
of  delicate  mensuration.  Whether  it  is 
level  or  not,  provided  its  slope  be  grad- 
ual and  even,  is  of  secondary  importance, 


50 

as  corrections  may  be  easily  applied  to 
cancel  the  effect  of  its  gradients. 

LENGTH    OP   THE    BASE. 

The  length  of  the  base  may  vary  from 
two  to  ten  kilometres.  In  the  opinion 
of  many  engineers  more  than  four  kilo- 
metres of  measured  length  is  zeal  gone 
astray,  for  the  advantages  of  accuracy 
gained  by  such  excess  would  be  obtained 
more  easily  by  devoting  the  extra  time 
to  a  more  elaborate  trigonometrical  de- 
velopment. No  arbitrary  rule  can  be 
applied  here,  however.  All  must  depend 
upon  the  judgment  of  the  engineer,  who 
will  consider  his  surroundings,  and  if 
they  are  favorable  for  a  slow  and  pro- 
gressive development,  a  short  base  will 
answer;  but  if  he  is  obliged  to  carry  his 
triangulation  from  the  base  stations  to 
the  distant  mountains  by  an  abrupt 
transition,  a  longer  one  will  be  required, 
to  prevent  too  great  acuteness  in  those 
remote  angles. 

INSTRUMENT   OF   MEASUREMENT. 

Since  rapidity,  as  well  as  accuracy,  is 


51 

an  object,  we  use  a  steel  tape,  ten  or  fif- 
teen metres  in  length,  as  a  measuring 
unit.  In  the  swivel  at  one  end  of  this 
there  is  a  thermometer  which  tells  the 
heat  to  which  the  tape  is  exposed  at 
any  time;  there  is  also  a  micrometer 
screw,  by  which  it  can  be  lengthened  or 
shortened  in  compensation  for  any  possi- 
ble change  of  temperature;  and  there  is 
a  dynamometer  attached  to  govern  the 
tension  applied,  which  should  amount  to 
three  or  four  kilograms,  being  at  every 
application  the  same  as  it  was  in  the  orig- 
inal test  for  length,  to  which  the  tape 
was  subjected. 

Thus,  as  this  apparatus  is  applied,  in 
the  process  of  measurement,  it  is  under 
a  constant  strain,  which  preserves  it 
from  the  error  from  sagging,  to  which 
all  flexible  cords  are  liable,  and  its  length 
is  always  corrected  to  meet  the  contrac- 
tion and  expansion  which  the  metal  is 
constantly  undergoing  as  the  tempera- 
ture varies.  Should  this  micrometer  be 
but  incompletely  graduated,  so,  for  in- 
stance, as  to  be  adjustable  only  for  every 


52 

five  or  ten  degrees  of  thermometric 
change,  or  should  it  even  be  wanting 
entirely,  very  good  results  can  still  be 
obtained  with  the  steel  tape  by  reading 
the  thermometer  at  every  application, 
and,  in  the  final  computations  for  length, 
making  the  necessary  temperature  cor- 
rections. Used  carefully  and  with  intel- 
ligence, this  instrument  is  one  of  the 
most  valuable  adjuncts  of  the  geograph- 
ical survey,  and,  in  the  hands  of  consci- 
entious and  interested  observers,  it  is 
capable  of  results  that  are  very  near  the 
exact  truth;  the  error  ought  not  to  ex- 
ceed one  centimeter  for  every  kilometer 
of  measured  distance. 

METHOD    OF   MEASUREMENT. 

The  mensuration  may  be  made  on 
wooden  plugs,  with  smooth,  flat  upper 
surfaces.  These  are  driven  firmly  into 
the  ground  along  the  alignment  at  inter- 
vals equal  to  the  length  of  the  tape,  and 
should  be  allowed  to  project  above  the 
earth  sufficiently  to  permit  this  cord  to 
swing  clear  of  all  inequalities  in  the 


53 

surface,  or  other  obstacles  between  the 
two  stations.  Or,  instead  of  these,  little 
stools  of  plank  may  be  used;  these 
should  have  short,  pointed  iron  legs,  to 
be  forced  into  the  ground,  so  as  to  hold 
the  wooden  block  firmly  in  position. 

When  all  things  are  ready  a  distance 
of  one  or  two  kilometers  can  be  meas- 
ured in  one  day.  But,  on  account  of  any 
possible  inefficiency  in  the  compensation 
for  temperature,  and  also  because  even 
the  best  assistants  are  liable  to  a  per- 
sonal equation  in  sticking  the  marking 
pin,  some  invariably  inserting  it  to  the 
right  of  perpendicular,  and  others  the 
reverse,  it  is  well  that  it  should  be 
measured  several  times,  and  by  different 
persons,  and  a  mean  of  the  results  taken. 
Then  it  should  be  leveled,  in  order  that 
each  tape-length  may  be  corrected  for 
its  gradient,  which  is  done  by  a  simple 
trigonometric  process,  and  finally  it  is 
reduced  to  its  corresponding  concentric 
arc  at  the  level  of  the  sea,  when  it  is 
ready  for  use  in  the  system  of  triangu- 
lation. 


54 


THE  ASTRONOMICAL  BASE. 

The  method  of  base-measurement  by 
astronomical  observation  is  sometimes 
resorted  to  in  geographical  surveying, 
but  this  process  will  be  noticed  here 
only  sufficiently  to  point  out  the  serious 
objections  that  there  are  to  its  use. 
Having  the  latitudes  of  the  two  ends  of 
the  base  and  the  azimuth  of  one  from 
the  other,  it  is  a  simple  matter  to  com- 
pute their  distance  apart.  This  seems  to 
afford  an  economy  of  labor,  over  the 
former  method,  that  involves  the  determ- 
ination of  the  latitude  and  longitude  of 
the  first  station,  the  azimuth  of  the  i  ase- 
line,  and  its  length  by  direct  measure- 
ment; this  one  requires  the  determina- 
tion of  the  latitude  and  longitude  of  the 
first  station,  the  azimuth  of  the  base- 
line, and  the  latitude  of  the  second 
station.  The  latter  is  apparently  the 
simpler  and  shorter  task,  and  since  both 
methods  are  based  upon  astronomical 
observation  they  would  appear  to  be 
equally  reliable.  But  they  are  not. 

Experience  has  long  since  taught  the 


55 


scientific  world  that  the  probable  error 
of  any  ordinary  astronomical  result  is 
several  meters  at  the  very  least,  and  that 
it  is  not  safe  to  put  absolute  reliance  in 
those  reports  which  give  a  latitude  down 
to  a  very  small  fraction  of  a  second. 
Now,  in  that  system  of  triangulation 
whose  position  is  based  upon  the  astro- 
nomical determination  of  one  point  only, 
an  error  of  a  few  meters  in  the  latitude 
of  that  point  will  not  do  material  injury. 
It  will  simply  displace  the  entire  trian- 
gulation scheme,  as  a  whole,  so  much  to 
the  north  or  the  south,  while,  since  the 
length  of  the  base,  or  measuring  unit  of 
the  proportions  of  *  this  scheme,  was 
accurately  found,  there  will  be  no  error 
in  these  proportions.  But,  in  the  astro- 
nomical measurement  of  a  base,  suppose 
its  two  terminal  points  to  be  in  their 
most  favorable  position,  that  is,  on  the 
same  meridian.  The  latitude  determina- 
tion of  the  southern  station  places  it 
several  meters  too  far  to  the  south  of 
its  true  position ;  that  of  the  other,  per- 
haps, makes  it  an  equal  distance  too  far 


56 

to  the  north.  Hence  it  follows  that 
there  is  an  error  in  the  length  of  the 
base  equal  to  the  sum  of  the  two  astro- 
nomical errors,  and  this,  in  the  develop- 
ment, is  multiplied  almost  indefinitely, 
being  repeated  in  any  side  of  triangle  as 
often  as  the  length  of  the  base  is  con- 
tained in  the  length  of  that  line.  This 
is  supposing  the  base  to  be  an  arc  of 
meridian;  the  greater  its  divergence 
from  the  meridian,  the  more  seriously, 
for  obvious  reasons,  will  an  error  in  the 
astronomical  determination  affect  the 
length  of  the  base.  An  astronomical 
base-line,  therefore,  should  only  be  used 
when  there  are  difficulties  which  make  a 
direct  measurement  impossible. 

THE    DEVELOPMENT    OF   THE    BASE. 

In  the  early  stages  of  the  develop- 
ment, occurring,  perhaps,  on  the  level 
surface  of  the  plain,  it  will  be  found 
necessary  to  use  artificial  signals.  Great 
tripods  of  frame-work,  ten  or  fifteen 
meters  high,  are  constructed,  leaving 
ample  space  within  for  the  observer  and 


5? 

his  instrument.     In  erecting  these,  care 
must  be  taken  that  none  of  the  legs  of 
the  tripod   interfere  with   the  view  to- 
wards any  of  the  proposed  triangulation 
stations.     Each  of  the  signals  terminates 
at  the  summit  with  a  flag-staff,  to  which 
voluminous   folds   of   white   muslin  are 
nailed,  while  the  body  of  the  steeple  is 
wrapped   with   the   same   material    and 
decked  with  loose  tatters  and  streamers, 
which,  by  their  ceaseless  flutter  in  the 
wind,  offer  occasionally  a  surface  from 
which  the  light  is  reflected  to  the  eye  of 
the  distant  observer.    The  same  purpose 
may  sometimes  be  better  served  by  the 
use  of  glittering  sheets  of  tin,  or  by  a 
cone  of  the  same  material.     These  meth- 
ods all  have  one  very  great  advantage 
over  the  more  accurate  heliotrope,  that 
is,  they  are  always  in  position,  and  ready 
for  observations    to   be   directed    upon 
them  at  any  time.     The  use  of  the  re- 
fleeting  mirror,  however,  unless  there  are 
a  number  of  heliotropes  in  the  field,  in- 
volves the  loss  of  much  time,  as  the  in- 
strument is  transferred  from  one  to  an- 
other of  the  neighboring  stations. 


58 

The  development  stations  should  be 
erected  in  conspicuous  places,  on  high 
ground  or  the  salient  angles  of  bluffs, 
that  the  observer  may  know  where  to 
direct  his  instrument  in  searching  for 
them,  as  it  is  extremely  difficult  to  pick 
out  the  faint  glint  of  a  few  yards  of 
muslin  on  the  broad  light  surface  of  a  re- 
mote plain.  As  the  development  con- 
tinues and  climbs  from  the  foot-hills  into 
the  high  and  peaked  mountains,  these 
natural  points  are  sharp  and  distinct 
enough,  being  projected  against  the  sky 
beyond,  and  the  labor  of  station-building 
ceases,  except  in  cases  that  are  very  un- 
favorable. 

True,  this  triangulation  by  natural 
points  is  not  so  precise  as  it  is  in  some 
geodetic  surveys,  and  especially  in  the 
surveys  of  coasts,  where  even  the  phase 
of  the  conical  signal  is  considered  too 
important  an  element  of  error  to  be  neg- 
lected; nor  is  it  wise  that  it  should  be  so, 
for  a  fault  of  a  few  meters  in  the  posi- 
tion of  a  mountain-top  in  the  remote  in- 
terior of  Brazil,  located  by  this  plan,  is 


59 

at  present  of  no  practical  consequence, 
and  the  nation  cannot  afford  to  purchase 
an  accuracy  imperceptibly  greater  than 
this  by  an  expenditure  that  would  many 
times  exceed  the  cost  of  this  method  of 
survey.  Considering  a  mountain  as  a 
land-mark  by  which  travelers  are  assured 
of  their  place  and  are  guided  as  they  go, 
it  will  be  seen  that,  to  men  who  travel 
by  land,  a  small  fraction  of  a  kilometer, 
in  latitude  and  longitude,  is  a  deviation 
which  they  cannot  notice;  to  the  voya- 
ger at  sea,  however,  the  exact  site  of  the 
sunken  rock  which  he  shuns  should  be 
known  to  him,  in  order  that  he  may  cer- 
tainly avoid  it.  This  is  why  the  coast 
survey,  in  most  countries,  precedes  that 
of  the  inland  in  the  degree  of  accuracy 
which  characterizes  it,  as  well  as  in  the 
amount  of  expense  which  attends  it. 

TRIANGULATION   BY   NATURAL   POINTS. 

It  must  not  be  inferred,  however,  that 
the  use  of  natural  points  in  triangulation 
necessarily  involves  a  serious  accumula- 
tion of  error.  In  general,  the  engineer, 


60 

looking  from  one  station  to  the  next,  can 
readily  cover,  with  the  thickness  of  the 
spider-line  of  his  instrument,  the  highest 
ground  of  the  distant  mountain,  and 
that  point  is  selected  as  a  correlative 
station,  because  that  is  the  spot  which 
can  be  most  easily  identified,  either  from 
a  distance,  or  upon  the  ground  itself. 
If  this  place  is  uncertain,  as  where  there 
are  a  number  of  pinnacles  of  equal  alti- 
tude, or  not  sufficiently  prominent,  as  in 
a  plateau  summit,  some  peculiar  object, 
as  a  solitary  tree,  or  an  isolated  boulder, 
should  be  chosen  as  a  center  upon  which 
to  sight.  If  the  profile  of  the  mountain 
has  but  little  curvature,  its  culminating 
point  is  usually  determined  by  a  pile  of 
rock,  a  clump  of  vegetation,  or  other 
body  upon  its  crest,  which,  although  it 
may  not  be  distinctly  visible  from  a  dis- 
tance, yet  has  the  effect  of  increasing 
the  apparent  altitude  at  that  precise 
locality.  In  the  same  way  the  useful- 
ness of  a  monument  of  rock,  which  a 
party  should  always  leave  behind  it 
upon  a  mountain,  as  a  signal  to  look 


61 

back  upon,  does  not  terminate  at  that 
distance  at  which  it  becomes  apparently 
invisible.  The  eye  will  still  be  im- 
pressed with  the  superior  elevation  of 
the  place  where  it  stands. 

If  the  round  top  of  a  mountain  is  per- 
fectly bare,  and  offers  none  of  these  ac- 
cidental aids  to  the  observer,  it  is  well 
for  him,  in  reading  his  first  angle  to  it,  to 
keep  the  horizontal  cross-wire  tangent  to 
the  surface,  while  he  makes  a  careful 
and  deliberate  search  for  its  highest 
point.  Having  decided  upon  this,  he 
brings  the  vertical  wire  upon  it,  and  then 
follows  down  the  thread  with  his  eye 
until  he  finds  it  bisecting  some  well- 
defined  body  in  the  field  before  him, 
such  as  a  corner  of  rock  or  the  trunk  of 
a  tree,  and,  in  his  repetitions  of  the 
angle  he  fixes  the  vertical  wire  always 
upon  this  object,  while  keeping  the  hori- 
zontal thread  tangent  to  the  surface.  In 
this  manner  he  secures  to  each  of  the 
following  readings  the  advantages  of  the 
prolonged  study  given  to  the  first,  and 
not  only  are  his  results  more  accurate, 


62 

as  a  whole,  but  they  also  agree  better 
among  themselves,  which  is  always  a 
source  of  gratification  to  the  engineer. 

THE    MOUNTAINS    OF    BEAZIL. 

In  those  lands  which  are  remote  from 
the  equator  the  summits  of  the  high 
mountains,  of  an  altitude  of  three  thou- 
sand metres  or  more,  are  above  all  vege- 
tation and  in  the  belt  of  perpetual  snow, 
and  their  occupation  is  a  work  of  great 
privation  and  exposure.  The  mountains 
of  Brazil  are  exempt  from  that  disad- 
vantage to  triangulation,  as  the  climate 
is  never  rigorously  cold  here,  and  the 
elevation  of  the  highest  land  is  less  than 
three  thousand  metres.  The  only  ob- 
stacles to  be  feared  here  are  the  oppo- 
site disadvantages  of  too  much  vegeta- 
tion, either  hiding  the  tops  of  the  peaks, 
or  embarrassing  the  ascent  to  them,  and 
too  little  height,  whose  result  is  liable  to 
be  a  system  of  round,  well-preserved, 
and  insufficiently  pointed  mountains. 
But  if  those  in  the  vicinity  of  Rio  de 
Janeiro  are  to  be  accepted  as  a  criterion, 


63 

nothing   more   could  be   desired  in  the 
way  of  natural  aids  to  triangulation. 

PROGRESS    OF   THE   TRIANGULATIOX. 

In  some  cases  it  may  be  absolutely 
necessary  to  send  a  party  in  advance  to 
erect  monuments  of  stone,  or  signals  of 
timber  upon  proposed  stations  which  are 
at  the  same  time  important  and  unfavor- 
able for  observations ;  or,  should  the 
mountain  be  covered  with  forest,  it  may 
be  necessary  to  send  axemen  to  clear 
away  all  but  the  largest  and  most  cen- 
tral of  these  trees.  Such  action,  how- 
ever, causes  a  vexatious  delay  on  the 
part  of  the  engineer,  and  is  contrary  to 
the  fundamental  principles  of  this 
method  of  survey,  whose  work  should 
be  a  steady  and  unretarded  progress, 
and  should  be  reconnoissance  and  com- 
pletion in  itself. 

From  the  top  of  his  first  high  mountain 
station  the  engineer  sees  his  allotted 
territory  spread  out  before  him,  and  he 
immediately  begins  to  lay  his  plans  for 
the  coming  season.  He  selects  two  dis- 


64 

tant  peaks,  which,  with  his  present 
station,  will  form  a  grand  triangle.  Be- 
yond these,  far  in  the  distance,  there  is 
yet  another,  and  these  four  constitute  a 
great  quadrilateral,  the  lengths  of  whose 
diagonals  may  each  l>e  determined  by 
two  independent  sets  of  observations, 
checking  each  other.  In  like  manner 
he  makes  the  circuit  of  the  horizon,  util- 
izing, as  best  he  can,  the  peaks  which 
rise  around  him. 

Although,  owing  to  the  many  obsta- 
cles and  unforeseen  difficulties  which  are 
experienced  in  traveling  through  an  un- 
known country,  he  may  be  compelled  to 
modify  and  alter  his  first  plans  very 
often,  yet  as  soon  as  he  abandons  one 
feature  of  his  scheme  he  immediately 
adopts  a  substitute  to  take  its  place. 
To  be  provided  for  such  an  emergency, 
if  a  distant  peak,  as,f  or  instance,one  of  the 
sharp  pinnacles  of  the  Organ  Mountains, 
should  appear  impossible  of  ascent,  he 
will  select  another  in  the  same  vicinity, 
and  consider  that  as  an  alternate  to  the 
first,  reading  angles  to  it  and  treating  it 


65 

in  all  respects  as  a  regular  station  as 
long  as  such  a  reserve  may  seem  neces- 
sary. 

In  proceeding  from  one  mountain  to 
the  next  he  surveys  all  of  the  interme- 
diate country,  his  course  being  governed 
by  the  advantages  and  obstacles  whieh 
present  themselves  from  day  to  day. 
His  route  should  never  be  an  arbitrary 
one,  determined  at  a  distance  and  weeks 
beforehand,  but  he  should  be  free  to  act 
upon  the  spur  of  the  moment,  following 
a  stream  to  its  source  here  and  stuvey- 
ing  a  lake  there,  according  as  these  geo- 
graphical features  may  be  encountered. 
If  these  features  are  depicted  on  maps 
already  made,  then  there  is  no  need  of  a 
second  survey  of  the  country;  if  they 
are  not,  he  is  not  likely  to  know  of  their 
existence  until  he  finds  them. 

EQUIPMENT  OF  THE  PARTY. 

Since  the  terminus  of  a  day's  survey 
cannot  always  be  advantageously  decided 
upon,  even  in  the  morning  on  which  it  is 
begun,  it  is  especially  desirable  that  th§ 


66 

party  may  carry  with  it  its  own  equipage 
and  supplies,  so  as  to  be  prepared  to 
camp  anywhere  that  night  may  over- 
take it.  As  it  is  a  part  of  the  policy  of 
geographical  work  that  the  engineer 
should  never  follow  the  same  route 
twice,  a  survey  carried  on  by  daily  ex- 
cursions from  fazendas,  settlements,  or 
other  fixed  points  of  supply,  returning 
to  this  base  by  the  same  road  in  the 
afternoon,  would  cost  a  great  waste  of 
time  and  energy.  The  necessary  outfit 
of  a  scientific  corps,  consisting  of  instru- 
ments, clothing,  cooking  utensils,  and 
provisions,  can  be  carried  by  a  train  of 
pack-mules  equal  in  number  to  the  peo- 
ple whom  they  accompany.  With  this 
equipment  the  party  are  independent, 
and  can  camp  anywhere  that  wood  for 
fuel,  forage  for  the  animals,  and  a  sup- 
ply of  water  are  found.  This  arrange- 
ment is  particularly  necessary  in  the 
occupation  of  a  mountain  station,  upon 
which,  for  successful  observation,  it  may 
be  imperative  to  arrive  at  an  early  hour 
in  the  morning  and  to  remain  through 


67 

the  greater  portion  of  one,  two,  or  three 
days.  From  a  camp  near  the  summit 
this  may  be  reached  in  an  hour  or  two; 
but  from  a  distant  base  almost  the  en- 
tire day  would  be  consumed  in  the  jour- 
ney to  and  fro. 

THE  TRIANGULATION  STATION. 

The  mountain  will  be  ascended  by  the 
engineer,  the  meteorologist,  and  such 
assistants  as  may  be  required  to  carry 
the  implements  of  the  work  and  the  food 
and  water  necessary  for  the  maintenance 
of  the  party,  and  to  build  the  stone 
monument,  which,  if  possible,  should 
always  crown  the  peak,  to  receive  the 
records  deposited  here,  to  assist  in  the 
future  identification  of  this  station,  and 
to  serve  as  an  object  upon  which  to 
direct  the  telescope  in  subsequent  ob- 
servations. One  day  will  be  a  sufficient 
time  of  occupation  for  the  ordinary 
triangulation  station,  provided  the 
weather  be  favorable.  To  the  more 
important  ones,  however,  it  may  be 
advisable  to  devote  two  days,  spending 


68 

one  night  upon  the  crest  in  astronomical 
observations  for  the  determination  of 
the  azimuth  of  some  line  radiating  from 
here;  this  will  serve  as  a  check  upon  its 
computed  value,  as  derived  from  the 
original  azimuth  determination  made  by 
the  astronomer  at  the  base-line.  In 
times  of  high  wind,  or  cloudy  and  stormy 
weather,  especially  liable  to  occur  upon 
the  summits  of  peaks,  it  may  be  several 
days  before  satisfactory  results  are  ob- 
tained, and  therefore  the  party  should 
always  go  well  equipped  for  a  prolonged 
stay  in  their  mountain  camp. 

PROFILE    SKETCHES. 

As  an  economy  of  time,  which  is  of 
the  greatest  value  here,  the  observer 
should  make  all  reasonable  haste  in  his 
operations.  Especially  is  this  so  in  his 
sketches,  over  which  he  must  not  linger, 
which,  if  he  is  anything  of  an  artist,  he 
will  be  sorely  tempted  to  do.  He  may 
see  before  him  broader  views  and 
scenery  more  grand  and  impressive  than 
ever  was  painted  yet,  but  picturesque 


69 

effects  are  no  business  of  his.  To  the 
geographer  of  artistic  tastes  there  is 
great  temptation  to  finish  his  sketch  by 
inserting  a  pine-tree  in  the  foreground, 
and,  perhaps,  an  eagle's-nest  in  the  tree; 
this  is  all  very  wrong,  as  such  dalliance 
may  cost  the  omission  of  that  far  distant 
peak,  which  is  printed  like  a  fine  point 
against  the  horizon,  and  which,  insignifi- 
cant and  low  as  it  appears,  is  yet  of 
vital  importance  to  his  scheme. 

His  sketch  is  perforce  but  the  outline 
and  skeleton  of  a  picture.  Two  con- 
verging straight  lines,  with  a  few  strokes 
of  shading,  hastily  thrown  in,  are  suffi- 
cient to  represent  the  ordinary  mountain 
peak.  Yet,  if  the  peak  should  possess 
any  oddity  or  marked  individuality  of 
shape,  this  feature  should  be  preserved 
and  even  magnified  in  the  drawing,  as  a 
key  to  the  identification  of  this  point 
when  seen  from  elsewhere  at  some  other 
time.  Since  any  mountain,  from  differ- 
ent points  of  view,  presents  phases  that 
are  quite  dissimilar,  it  is  one  of%  the 
greatest  difficulties  of  triangulation  to 


70 

make  sure  of  the  identity  of  a  station 
previously  occupied,  or,  where  there  are 
a  number  of  observers  in  the  field,  to  se- 
cure uniformity  in  the  choice  of  the  same. 

CONTOUR   DRAWINGS. 

The  expert  geographer  is  proficient  not 
only  in  rapid  profile  but  also  in  contour 
drawing,  and  on  every  mountain  station 
he  executes  a  contour  plot  of  that  scope 
of  country  which  he  sees  beneath  his 
feet,  and  of  whose  conformation  he  is 
reasonably  certain.  But  in  the  prepara- 
tion of  this  local  plot  he  should  not  be 
too  comprehensive,  and  go  beyond  the 
bounds  of  certainty  into  the  outer  limits 
of  conjecture.  Every  mountain  is  sur- 
rounded by  valleys,  on  whose  farther 
side  are  other  ranges  perhaps  as  high  as 
this,  and  they  form  the  limit  beyond 
which  no  contour  sketch  should  presume 
to  go,  else  it  becomes  conjectural  and 
unreliable.  It  may  include  those  en- 
virons of  valleys,  with  a  periphery  of  the 
foot-hills  which  are  beyond  them,  and  an 
indication  of  the  canons  which  indent 
the  same,  but  no  more. 


71 

In  the  office  a  contour  sketch  is  ac- 
cepted as  truthful  evidence  of  the  ground 
as  it  really  is,  while  a  profile  drawing  is 
considered  only  a  copy  of  the  country  as 
it  appears  to  be,  when  uncorrected  for 
the  illusions  of  perspective,  and  is  studied 
and  deciphered  accordingly.  Looking 
abroad  from  this  station,  the  successions 
of  distant  ranges,  which  are  in  reality 
separated  by  broad  interspaces  of  valley 
and  plain,  are  projected  into  a  dense  and 
circular  wall,  apparently  unbroken  by 
pass  or  intermission,  whose  serrated  out- 
line is  seemingly  as  continuous  as  the 
horizon.  It  is  an  error  to  which  the 
human  sight  and  judgment  are  subject, 
and  so,  in  orographic  delineation,  the 
impressions  of  the  eye  are  to  be  received 
with  caution,  and  only  the  readings  of 
the  theodolite  are  to  be  accepted  in  full 
faith. 

PHOTOGRAPHS. 

As  a  supplement  to  the  pencil  of  the 
engineer,  the  photographer's  camera  can 
often  be  used  to  good  advantage  in  se- 
curing, in  their  true  proportions,  the 


72 

many  details  of  geological  structure 
which  are  necessarily  omitted  from  a 
hasty  sketch.  In  the  best  geographical 
delineation  of  a  country,  a  series  of 
photographs  are  almost  indispensable, 
as,  aside  from  affording  much  material 
for  the  filling  in  of  a  map,  they  reveal 
the  nature  of  the  surface  which  they 
represent,  showing  whether  it  is  regular 
or  broken,  well-preserved  or  eroded, 
whether  a  cliff  is  impassable  or  easy  of 
ascent,  and  whether  a  coast  is  smooth 
and  sandy,  or  irregular  and  rocky.  All 
of  these  conditions  should  be  made  to 
appear  in  every  good  map,  whether  in 
contour  lines  or  hachures,  and  particu- 
larly so,  when,  as  in  this  case,  the  map  is 
intended  as  a  basis  for  geological  repre- 
sentation. 

READING   THE    ANGLES. 

The  instrument  of  triangulation  is  a 
theodolite,-  whose  accuracy  and  weight 
increase  with  the  minuteness  of  the 
graduation,  but,  in  this  work,  in  which 
rapidity  and  ease  of  transportation  are 


73 

to  be  considered,  there  comes  a  limit  be- 
yond which  it  is  imperative  to  sacrifice 
nicety  to  portability.  This  is  reached 
when  the  limb  is  graduated  so  as  to  dis- 
criminate to  ten  seconds  of  arc,  between 
which  divisions  the  observer  may  esti- 
mate to  every  intermediate  five  seconds. 
With  this  he  reads  and  repeats  the 
angles,  singly  and  in  combinations,  that 
lie  between  the  visible  points  of  the 
triangulation  scheme.  It  is  advisable  to 
make  at  least  six  determinations  of  each 
angle  upon  each  of  the  two  verniers  of 
the  instrument,  amounting  to  twelve 
repetitions  in  all.  The  greater  the  num- 
ber of  readings  from  which  the  mean  is 
derived,  the  less  will  be  the "  probable 
error  of  observation  affecting  that  mean. 
The  observer  may  complete  the  repe- 
tition of  each  angle  by  itself,  or,  what  is 
more  convenient,  he  may  read  them  in 
conjunction,  by  making  six  complete  cir- 
cuits of  the  horizon.  In  either  case  the 
graduated  limb  of  the  theodolite  will  be 
turned  30°  in  azimuth  at  every  return  to 
the  initial  point.  In  this  manner  each 


74 

angle  is  read  upon  twelve  different  and 
equi-distarit  divisions  of  the  circle,  and 
the  faults  arising  from  eccentricity  or 
imperfect  graduation  are  reduced  to  a 
minimum. 

The  most  opportune  moments  of  the 
day  will  be  devoted  to  this  important 
task,  and  all  other  duties  will  be  neg- 
lected for  this.  Successful  triangulation 
demands  perfect  quiet  and  a  clear  hori- 
zon. In  a  dense  and  hazy  atmosphere, 
or  in  a  region  of  low  clouds,  the  observer 
may  find  his  opportunity  in  the  evening 
or  early  morning,  when  the  sun  is  be- 
hind the  hills,  and  the  rim  of  the  earth 
is  seen  in"  silhouette  against  the  rosy 
background  of  the  sky. 

SUBORDINATE  ANGLES. 

Upon  the  triangulation  station  the 
engineer  also  reads  angles  for  the  direc- 
tion of  the  spurs  which  project  from 
here  and  of  the  streams  that  debouch 
from  here,  estimating  the  distances  of 
geographical  features  in  his  immediate 
vicinity.  How  far  he  may  trust  to  his 


75 

judgment  in  this  respect,  will  be  determ- 
ined by  the  circumstances  by  which  he 
is  surrounded.  It  is  the  engineer's  duty 
to  make  the  best  map  of  a  country  that 
is  possible  with  the  advantages  at  his 
command,  and  if  he  should  see  before 
him  a  tract  of  country,  distant  even  ten 
or  twenty  kilometres,  which  he  will 
never  see  again,  he  should  take  note  of 
it  on  his  contour  plot;  but  if  he  knows 
that  some  future  route  of  his  will  cross 
it,  he  can  afford  to  neglect  it  now. 

In  addition  he  takes  readings  to  infe- 
rior elevations  which,  although  they 
may  never  be  occupied  for  reciprocal  ob- 
servations, may  yet  be  located  by 
intersections  from  two  or  more  triangu- 
lation  stations.  Some  point,  or  "tit," 
standing  on  the  edge  of  an  abrupt  bluff, 
where  the  rapid  descent  begins,  is  used 
as  a  means  of  marking  the  end  of  a 
neighboring  mountain  range.  A  solitary 
butte  on  the  plain,  insignificant  in  itself, 
is  very  useful  in  determining  the  locus 
of  the  stream  which  flows  by  the  side  of 
it.  A  promontory,  jutting  into  the  con- 


76 

fluence  of  two  rivers,  is  instrumental  in 
fixing  the  place  of  their  union.  Sights 
are  also  taken  to  the  junctions  of 
streams,  the  mouths  of  canons,  and  to 
the  church  or  other  central  object  of  a 
distant  village.  A  spot  of  green  on  the 
desert,  evidence  of  a  spring  of  water 
there,  is  located,  for  it  will  perhaps  be 
camping-ground  some  day  for  himself  or 
his  co-laborers.  A  minute  patch  of 
white  lake-bed,  or  red  escarpment,  or  a 
solitary  tree,  is  sighted  upon,  because  on 
such  a  day  he  made  an  odometric  sta- 
tion there,  and  this  sight  will  serve  to 
check  his  position. 

NOMENCLATURE. 

In  his  note-book  and  mind  he  has 
dubbed  all  of  these  things  with  graphic 
titles,  or  designated  them  by  letters  of 
the  alphabet,  and  by  these  tokens  he  will 
know  them  when  he  sees  them  again. 
But  this  system  of  names  is  only  a 
transient  device  for  the  assistance  of 
himself  and  those  who  work  in  concord 
with  him,  and  should  not  appear  upon 


the  printed  sheet  to  the  exclusion  of  tae 
native  and  established  nomenclature  of 
the  country,  which  should  be  investigated 
as  far  as  possible,  and,  upon  the  final 
maps,  should  be  adopted  in  preference 
to  the  arbitrary  naming  of  any  one  man. 
The  usefulness  of  a  map,  as  a  guide  to 
the  traveler,  is  in  a  great  degree  invali- 
dated by  a  nomenclature  which  is  at 
variance  with  that  in  use  upon  the  ground 
itself.  Perhaps  the  modern  geographer 
is  guilty  of  no  more  common  and  high- 
handed outrage  against  right,  conven- 
ience, and  beauty,  than  by  ignoring  the 
appropriate  titles  which  abound  in  every 
country,  however  wild  and  uncivilized, 
and  attaching  his  own,  or  by  mutual  and 
tacit  agreement,  the  names  of  his  com- 
rades, to  the  mountains  of  that  land, 
thus  announcing  themselves  to  the  world 
as  nostrums  are  advertised  on  the  pyra- 
mids. 

THE  TOPOGEAPHICAL  STATION. 

All  of  the  preceding  description  that 
does  not  refer  to  the  triangulation  pro- 
cess is  also  pertinent  to  the  topographical 


78 

tation.  This  term  is  applied  to  those 
isolated  stations  of  survey,  apart  from 
the  route  of  the  odometer,  and  interme- 
diate to  the  points  of  primary  triangula- 
tion.  They  are  more  numerous  than  the 
primary  stations,  being  usually  scattered 
over  the  country  at  intervals  of  not 
more  than  twenty  kilometres,  but  are 
less  important,  since  there  is  no  great 
responsibility  of  accuracy  resting  upon 
them.  The  topographical  stations  cor- 
respond, in  position  and  numbers,  with 
the  secondary  triangulation  stations  of  a 
more  elaborate  geodetic  survey. 

A  SECONDARY  TRIANGULATION. 

Even  here  the  topographical  station 
may  be  made  a  point  in  a  subordinate 
scheme  of  triangulation  if  its  situation  is 
elevated,  distinct,  and  capable  of  recog- 
nition from  a  distance.  Of  course,  it  is 
desirable  that  every  occupied  station 
should  subsequently  be  made  an  object 
of  reciprocal  observations,  and  the  engi- 
neer should  neglect  no  opportunity  to 
confirm  his  position  in  this  manner. 


79 

Each  point  thus  fixed  becomes  the  center 
of  a  plexus  of  triangles,  of  each  of  which 
the  three  angles  have  been  observed; 
the  total  error  of  observation  in  these 
three  angles  becomes  apparent,  and  the 
computer  is  enabled  to  distribute  it  judi- 
ciously among  them  before  he  proceeds 
to  the  computation  of  the  sides. 

For  this  reason  the  observer  upon  any 
topographical  station  will  make  careful 
search  for  other  points  which  he  may 
have  occupied  or  may  contemplate  oc- 
cupying, and  will  be  more  than  usually 
cautious  in  reading  angles  to  them.  On 
his  return  to  the  office,  at  the  end  of  the 
season,  he  will  pick  out  from  the  multi- 
tude of  his  notes  as  many  complete  tri- 
angles as  he  may  have  observed,  and 
these  will  be  so  much  gain  attained  at  a 
cost  of  but  little  extra  labor.  But  if  he 
makes  it  imperative  upon  himself  to 
carry  on  a  complete  and  systematic  tri- 
angulation  within  the  first,  the  additional 
refinement  gained  will  by  no  means  com- 
pensate him  for  the  disadvantages  of 
reconnoissance  and  delay  which  this  in- 
volves. 


80 

It  is  safe  to  say  that  it  is  a  longer  and 
more  laborious  work  to  accomplish  an 
unbroken  secondary  triangulation  than 
a  primary,  as  the  stations  are  more  nu- 
merous, less  elevated  and  conspicuous, 
and  oftener  in  the  shadow.  On  the 
other  hand,  the  results  are  by  no  means 
so  valuable.  The  primary  triangulation 
sustains  the  general  and  continued  accu- 
racy of  the  survey;  the  secondary  does 
little  more  than  to  insure  the  individual 
positions  of  its  own  stations. 

POSITION     OF    THE    TOPOGRAPHICAL    STA- 
TION. 

Although  not  necessarily  a  point  in 
the  triangulation  proper — the  site  of  the 
topographical  station  must  afford  angu- 
lar data  sufficient  for  the  determination 
of  its  position  by  the  three-point  problem. 
After  that,  its  predominant  idea  is  that 
it  is  a  means  of  local  geography,  or  to- 
pography, and  a  center  for  a  series  of 
contour  sketches.  In  addition  to  these 
detailed  plots  of  the  country  in  the  im- 
mediate vicinity,  profile  drawings  of  the 


81 

more  distant  regions  are  made.  Then, 
by  lines  of  sight,  which  shall  be  intersect- 
ed by  other  rays  from  other  topographical 
or  triangulation  stations,  the  most 
prominent  features  within  a  radius  of 
twenty  or  thirty  kilometres  are  crossed, 
and,  as  a  precaution,  angles  are  also  read 
to  all  eminent  points  visible  at  a  greater 
distance,  even  to  the  horizon,  as  they 
may  come  into  use  in  some  future  di- 
lemma in  map-drawing. 

While  the  site  of  the  topographical 
station  should  be  as  elevated  and  marked 
as  possible,  yet  any  hill,  however  humble 
and  inconspicuous,  or  even  the  level  sur- 
face of  a  plain,  may  serve  this  purpose? 
provided  that  there  be  three  triangula- 
tion stations,  or  other  known  points,  visi- 
ble, and  there  is  any  useful  information 
to  be  gained  by  lingering  here.  A  few 
hours  are  usually  enough  for  its  occupa- 
tion, and  the  route  between  points  of 
triangulation  should  be  marked  at  regu- 
lar intervals  by  the  monuments  of  these 
stations.  It  is  a  good  plan  for  the  en- 
gineer to  make  a  practice  of  diverging 


82 

from  his  route  at  some  point  in  each 
day's  odometric  survey,  and,  ascending 
a  suitable  eminence  close  at  hand,  make 
a  topographical  station  there.  As  far  as 
a  general  rule  can  be  given  for  the  oc- 
currence of  mountain  stations,  it  is  advis- 
able for  the  party  to  advance  by  linear 
survey  every  second  day,  remaining  in 
camp  on  each  alternate  day,  while  the 
engineer  ascends  some  peak  in  the  vicin- 
ity for  the  purpose  of  establishing  a 
topographical  or  triangulation  station 
there. 

The  -  large  triangulation  theodolite 
should  be  used  in  the  more  important 
topographical  stations,  or  those  which 
may  possibly  be  treated  as  points  in  a 
secondary  triangulation,  but,  for  the  sake 
of  convenience,  the  small  route  transit 
must  be  made  to  suffice  for  those  which 
are  made  in  the  course  of  the  daily 
march. 

THE    ODOMETRIC,  OR    MEANDER    SURVEY.* 

The  meander  survey  is  useful  as  an 

*  Note  to  the  Portuguese  Edition.— This  term,  which  is 
now   firmly   grounded    in    the    technical   language   of 


83 

adjunct  to  the  triangulation,  filling  up 
its  skeleton  with  that  'detailed  informa- 
tion which  alone  can  give  practical  and 
popular  value  to  a  map.  It  determines 
the  courses  of  valleys  and  streams,  the 
routes  of  roads  and  trails,  the  peripheries 

geographical  surveying  in  the  United  States,  is  a  mis- 
nomer, and  therefore,  in  introducing  a  corresponding 
one  into  the  Portuguese,  it  will  be  well  to  adopt  some 
more  appropriate  expression.  For  this  reason  "  odomet- 
ric  survey"  will  be  used  to  designate  line  surveys  in 
which  the  odometer  takes  part,  and  "route  survey" 
(caminhamento)  as  a  general  term,  to  include  not  only  the 
above,  but  also  those  in  which  distances  are  determined 
by  time,  by  the  chain  where  that  method  is  employed,  or 
by  paces,  whether  of  man  or  horse,  and  whether  re- 
corded by  the  pedometer  or  by  direct  counting. 

As  the  meander  survey  is  understood,  where  this  ex- 
pression is  used,  it  is  simply  any  survpy  following  a  zig- 
zag line,  whose  angles  in  general,  are  alternately  salient 
and  re-entrant,  as  the  line  accommodates  itself  to  the 
route  of  travel.  But  this  word  "  meander,"  having  been 
derived  from  the  river  of  the  same  name,  in  ancient 
Phrygia,  which  was  celebrated  for  its  winding,  sinuous 
course,  literally  means  "abounding  in  curves."  It  will 
thus  be  seen  that  the  more  a  survey  approaches  to  a  true 
meander,  the  farther  it  departs  from  the  first  principles 
of  accurate  linear  surveying,  which  dictate  that  it  shall 
consist  of  straight  lines  and  angles  only.  Since  it  is  al- 
ways to  be  regretted  when  a  survey  is  confined  to  a  true 
meand*er  line,  as  for  instance,  in  tracing  the  course  of  a 
road  along  and  up  the  Fide  of  a  mountain  range,  so  it  is 
also  a  matter  of  regret  that  this  word  should  have  been 
introduced  into  the  language  of  engineering,  apparently 
sanctioning  a  faulty  survey. 


84 

of  lakes  and  basins,  and  the  distances 
between  springs  of  water,  villages,  areas 
of  pasture,  fords  of  rivers,  and  other 
points  of  interest  to  the  future  traveler. 
Finally,  it  is  a  commendable  occupation 
for  the  engineer  while  on  his  way  from 
one  mountain  station  to  the  next,  and, 
since  it  occasions  no  delay  in  the  general 
progress  of  the  work,  as  the  engineer 
can,  as  a  rule,  meander  as  much  road  as 
his  pack-train  can  travel  in  one  day,  its 
results  are  net  gain  to  the  survey. 

In  the  theoretical  journey  of  this  kind, 
the  engineer  would  follow  the  edge  of 
the  dividing  ridge  from  one  station  to 
the  next,  from  which  lofty  promenade 
he  could  see  the  earth  like  an  extended 
scroll  beneath  his  feet,  and  make  a  sur- 
vey that  would  be  exhaustive  and 
complete.  But  in  the  real,  hard  prac- 
tice, he  finds  this  path  an  impracticable 
one,  for  it  is  broken  by  precipices  and 
blocked  by  abutments  often  a  hundred 
metres  or  more  in  height.  His  easiest 
route  of  travel  is  by  the  side  of  flowing 
water,  whose  tendency  it  is  to  erode  aft- 


85 

rupt  cliffs  and  soften  steep  gradients 
into  an  average  and  even  slope.  Be- 
sides, along  the  streams  there  are  trails 
made  by  the  wild  animals  which  come 
here  for  drink  and  covert,  and  by  the 
people  of  the  country  who  come  hither 
to  hunt  and  fish.  Therefore,  if  the*  de- 
tour be  not  too  great,  the  most  expedi- 
ent route  from  mountain  to  mountain,  is 
down  one  valley  and  up  another,  and 
the  geographer  who  traverses  a  valley 
without  taking  some  sort  of  a  survey  of 
it,  is  culpably  negligent  of  his  duty. 
On  the  other  hand,  if  in  a  block  of 
mountains  the  pre-eminent  peaks  be  oc- 
cupied, and  the  streams  which  emanate 
therefrom  be  meandered,  nothing  more 
is  needed  for  a  most  excellent  geograph- 
ical map  of  that  country. 

THE    MEANDER   TRANSIT. 

It  is  supposed  that  all  transportation 
of  outfit,  and  all  travel,  even  in  the  me- 
ander survey,  is  accomplished  on  the 
backs  of  horses  or  mules.  Riding  in 
the  saddle,  the  surveyor  can  devote  but 


86 

one  hand  to  the  grasp  and  protection  of 
his  instrument,  the  feet  of  whose  tripod 
rest  in  a  holster  attached  to  the  left 
stirrup.  To  facilitate  his  secure-  hold, 
the  members  of  the  tripod  are  thirds  of 
a  cylinder,  which  fold  into  the  smallest 
possible  compass,  and  are  easily  held  in 
the  grip  of  one  hand. 

The  instrumental  part  of  the  meander 
transit  is  neat,  solid,  and  compactly 
constructed.  Its  graduated  limb  is  of 
small  diameter,  and  its  horizontal  ver- 
nier reads  to  minutes  only,  which  is  all 
very  well,  since  no  smaller  divisions  can 
be  plotted  on  the  map.  This  graduation 
is  used  in  the  occupation  of  topograph- 
ical stations,  at  those  meander  stations 
where  the  view  is  extended  enough  to 
make  it  profitable  to  linger  an  hour  or 
so  in  the  accumulation  of  notes  and 
sketches,  and  at  all  those  which  are 
three-point  stations  as  well.  But  in  the 
general  survey,  not  the  vernier-plate, 
but  the  compass  needle,  is  used,  on  ac- 
count of  its  greater  convenience.  The 
compass  box  is  graduated,  from  zero  at 


8V 

the  north,  around  by  the  left  to  360°  at 
the  north  again,  so  that  a  reading  of  90° 
corresponds  to  magnetic  east,  and  270° 
to  west.  The  field  records  are  kept 
in  this  manner,  and  in  the  office  the  de- 
clination of  the  needle  is  first  applied  to 
each  bearing^  after  which  it  is  reduced 
to  its  true  direction,  preparatory  to  the 
plotting. 

THE  ODOMETEB. 

The  distances  from  station  to  station 
of  the  meander  are  measured  by  the 
odometer,  an  implement  of  survey  which, 
in  some  of  its  forms,  has  been  long  in 
use  in  Europe,  and  has  of  late  years  re- 
ceived especial  attention  and  improve- 
ments in  the  reconnoissances  and  other 
geographical  surveys  carried  on  by  the 
War  Department  of  the  United  States 
of  North  America.  In  this  service  it 
has  been  adapted  to  the  severe  condi- 
tions of  travel  in  a  new  country.  It  has 
been  strengthened  so  as  to  withstand 
any  shock  or  fall  to  which  it  may  be 
subject.  The  recording  apparatus  is 


88 

made  so  compact  and  simple  that  there 
is  no  danger  of  disarrangement  there. 
Instead  of  the  old  laborious  process  of 
pushing  it  by  hand,  the  wheel  has  been 
fitted  with  shafts,  so  as  to  be  drawn  by 
a  mule,  and  so  efficient  is  the  method  of 
attachment  that  the  odometer  can  follow 
any  route,  however  rough,  precipitous, 
or  narrow,  that  will  admit  of  the  passage 
of  a  pack-mule. 

In  its  simplest  and  best  form  the 
odometer  vehicle  is  a  solitary  wheel,  a 
little  more  than  a  meter  in  diameter,  or 
about  the  size  of  a  light  carriage- wheel. 
It  is  strongly  constructed  of  the  best 
material,  and  is  braced  by  opposite  in- 
clinations of  alternate  spokes,  so  as  to  be 
uninjured  by  the  heaviest  jars  and  col- 
lisions. A  pair  of  shafts  are  attached  to 
it,  and  into  these  a  strong  and  steady 
mule  is  firmly  harnessed  by  straps  from 
above  and  underneath.  The  vehicle  is 
close  in  the  rear  of  the  animal,  and  the 
shafts  are  made  short  and  heavy,  and  in 
this  manner  the  wheel  is  preserved  in  a 
plumb  or  upright  position  as  it  runs,  not 


89 

swaying  from  side  to  side.  The  length 
of  the  circumference  of  the  wheel  being 
accurately  known  and  the  number  of 
revolutions  being  recorded  by  the  at- 
tached apparatus,  it  is  a  simple  matter 
to  learn  the  distance  between  any  two 
points. 

The  recording  instrument  hangs  in  a 
cylindrical  box  which  is  strapped  to  the 
wheel.  It  consists  of  a  mechanical  com- 
bination attached  to  a  heavy  block  of 
metal,  whose  center  of  gravity  is  at  one 
side  of  the  axis  to  which  it  is  suspended. 
As  it  is  free  to  revolve  upon  this  axis  it 
always  maintains  a  vertical  position, 
while  its  box  turns  with  the  wheel,  and 
the  apparatus  scores  the  number  of 
revolutions,  of  which  it  is  capable  of  re- 
cording 9900,  or  a  distance  of  about 
forty  kilometers,  when  it  begins  anew. 

USEFULNESS  OF   THE  ODOMETEK. 

This  detailed  description  of  the  odo- 
meter is  in  accordance  with  the  promise, 
made  in  the  early  part  of  this  article,  to 
dwell  upon  the  novel  features  of  this 


90 

work,  even  to  the  exclusion  and  apparent 
neglect  of  others,  already  well-known, 
which  are  really  of  greater  importance. 
Still  it  would  be  difficult  to  over-esti- 
mate the  usefulness  and  practical  value 
of  this  instrument.  It  requires  but  little 
technical  knowledge  to  use  it  and  to 
conduct  the  meander  survey  which  ac- 
companies it,  and  any  person  educated 
in  the  simplest  rudiments  of  surveying 
is  competent  for  this  kind  of  work. 

For  this  reason  every  party  of  scien- 
tific exploration  and  reconnoissance, 
every  preliminary  survey  for  railways, 
and  every  marching  body  of  troops 
should  consider  its  outfit  incomplete 
without  the  implements  of  an  odometric 
survey.  Aside  from  the  mass  of  notes 
and  sketches  that  would  be  accumulated 
by  them,  and  the  itinerary  maps  that 
would  result,  in  the  item  of  distances 
alone  the  country  would  be  more  than 
repaid  for  the  cost  of  these  surveys.  As 
a  means  of  mensuration  the  odometer 
will  determine  distances  en  route,  as  the 
wagon  travels,  more  truthfully  than  the 


91 

chain  itself.  These,  being  published, 
are  of  profit,  not  only  to  the  ordinary 
traveler,  but  also  to  the  general  govern- 
ment, whose  agents  and  officials,  in  one 
capacity  or  another,  are  constantly  pas- 
sing to  and  fro. 

ERRORS    OF   THE    ODOMETRIC    SURVEY. 


is  there  any  very  great  error  in 
the  ordinary  surveys  which  the  odome- 
ter is  likely  to  be  called  upon  to  perform. 
Having  the  geographical  positions  of 
two  towns  forty  kilometres  apart,  they 
may  be  connected  by  an  odometric  sur- 
vey, the  plot  of  which  can  be  adjusted 
between  these  two  positions  so  that  no 
intermediate  points  will  be  appreciably 
out  of  place  on  a  map  of  the  usual  scale. 
Since  this  is  a  map  for  practical  use  and 
for  the  public  good,  it  fulfills  its  pur- 
pose as  well  as  if  its  distances  had  been 
measured  by  the  most  refined  methods. 

The  great  objection  to  its  use  is  the 
tendency  towards  the  accumulation  of 
error  in  an  odometric  meander,  and  the 
farther  it  is  from  the  known  point  which 


92 


is  its  origin,  the  greater  is  the  probable 
error  of  any  position  determined  by  it. 
Therefore,  in  a  prolonged  journey,  or  in 
a  general  survey  of  the  country,  the 
odoraetric  position  should  frequently  be 
verified,  or  checked  and  rectified,  by  con- 
nection with  known  points.  This  can  be 
accomplished  by  making  a  station  at 
some  point  on  a  railway,  boundary,  or 
other  line  of  accurate  survey  ;  by  astro- 
nomical observation,  which,  however,  if 
taken  with  a  sextant,  is  often  less  relia- 
ble than  the  meander  itself;  or  by  mak- 
ing a  meander  station  dependent  upon 
the  accompanying  triangulation,  by 
means  of  the  three-point  problem.  The 
last  method,  which  is  by  far  the  most 
reliable,  will  be  explained  further  on. 

ERROR    OF    DIRECTION. 

The  meander  is  affected  by  error  of 
two  kinds,  of  direction,  and  of  distance. 
The  former,  in  its  most  serious  nature,  is 
incurred  in  the  survey  of  a  tortuous  val- 
ley, whose  general  course  must  be  ac- 
cepted, or  in  crossing  a  timbered  coun- 


93 

try,  or  a  pathless  plain,  where  the  sur- 
veyor is  in  a  constant  state  of  uncer- 
tainty as  to  whither  he  is  to  go,  or,  tak- 
ing a  back-sight,  as  to  whence  he  has 
come.  Sometimes  the  engineer  is 
obliged  to  keep  his  eye  on  the  sun  and 
get  a  general  idea  of  the  course  from 
that.  Or,  in  traversing  a  dense  forest, 
he  may  find  himself  compelled  to  resort 
to  the  paradox  of  sighting  upon  a  sound; 
that  is,  he  allows  the  pack-train  to  keep 
a  certain  distance  in  advance,  and  from 
time  to  time  he  directs  his  telescope  to 
the  tinkling  of  the  bell  which  is  carried  by 
the  horse  that  leads  the  train.  It  must 
be  confessed  that  these  make-shifts  are 
loose  methods  of  survey,  but  they  are 
better  than  none,  since  they  give  the 
prominent  directions  and  the  distances 
between  streams,  divides,  etc.,  and 
months  afterwards,  when  the  engineer 
comes  to  make  the  map  and  lay  down 
upon  it  the  trail  of  that  day's  march,  he 
will  find  the  poorest  and  most  incom- 
plete notes  more  reliable  than  his  present 
memory  and  judgment. 


94 

Even  under  the  most  favorable  cir- 
cumstances it  will  seldom  be  possible  to 
direct  the  telescope  with  greater  pre- 
cision than  to  the  nearest  degree,  nor,  as 
a  consequence,  will  it  ever  be  worth 
while  to  record  any  fraction  of  a  revolu- 
tion in  the  odometer.  A  road  does  not 
usually  change  direction  by  an  abrupt 
angle,  but  by  a  gradual  curve,  and  the 
bearing  is  made  approximately  tangent 
to  that  curve.  Or,  in  the  survey  of  a 
stream,  it  is  not  known  on  which  side 
the  trail  will  run  at  some  point  a  kilo- 
metre in  advance,  and  so  the  approxi- 
mate center  of  the  valley  is  accepted. 
But  if  there  should  be  a  solitary  tree, 
bush,  house,  rock,  or  other  prominent 
object  fortunately  situated  for  a  station, 
the  course  will  be  made  closely  tangent 
to  that,  a  reading  of  instruments  will  be 
taken  upon  arriving  there,  and,  going  on 
to  the  next  station,  the  engineer  will 
take  a  back-sight  to  the  same  point.  In 
general  the  system  of  back-sights  will 
be  found  more  satisfactory  than  that  of 
foresights,  as  it  is  easier,  on  a  strange 


95 

route,  to  tell  whence  you  have  corne  than 
to  decide  where  you  are  going. 

ERROR    OF   DISTANCE. 

This  error  of  direction,  it  will  be  seen, 
is  thrown  by  the  law  of  chance  alter- 
nately to  the  right  and  left  of  the  true 
line,  and  so  has  a  tendency  in  its  elements 
towards  mutual  compensation,  and  in  a 
measure  it  corrects  itself.  But  not  so 
the  error  of  distance,  which  is  always 
plus,  and  cumulatively  so.  The  test  of 
the  odometer  wheel,  by  which  its  num- 
ber of  revolutions  per  kilometre  is  ascer- 
tained, is  made  upon  a  level  surface  and 
along  a  staked  alignment,  giving  a  re- 
sult almost  absolutely  correct.  In  prac- 
tice, however,  the  vehicle  climbs  acclivi- 
ties of  every  grade,  tacks  hither  and 
thither  as  it  follows  the  trail  up  the 
mountain,  winds  incessantly  in  its  route 
through  the  forest,  and  is  disturbed  by 
frequent  jolts  and  collisions  along  the 
rocky  floor  of  the  canon.  In  a  theo- 
retical traverse  the  straight  line  between 
any  two  stations  is  determined,  but  in  an 


96 

odometer  survey  the  measuring  imple- 
ment usually  follows  a  beaten  path,  and 
the  route  distance,  by  road  or  trail,  is 
rarely  the  shortest  distance  between  two 
points.  Hence  an  "overrun"  in  its 
record,  which  can  only  be  remedied,  and 
that  approximately,  by  the  judgment  of 
the  surveyor,  who  is  taught  by  experience 
to  estimate  very  closely  the  surplus  in  a 
given  run,  and  who  applies  a  correction 
accordingly. 

Still,  to  such  perfection  has  the  odo- 
meter survey  been  brought,  that  it  is  a 
common  occurrence  for  a  skilled  worker 
to  meander  a  closed  circuit  of.  one  hun- 
dred kilometres,  and  plotting  the  route, 
to  find  the  plot  also  close  within  a  small 
fraction  of  a  kilometre.  Even  this  error, 
being  judiciously  distributed  in  the  pro- 
cess of  adjustment,  different  weights 
being  assigned  to  different  runs,  accord- 
ing to  their  probable  accuracy,"  may  be 
reduced  so  as  to  be  practically  imper- 
ceptible. 

OCCURRENCE  OF  MEANDER  STATIONS. 

No  general  rule  can  be  given  for  the 


97 

frequency  of  meander  stations,  but  in 
ordinary  country  they  will  average  per- 
haps one  to  the  kilometre.  In  this  all 
will  depend  upon  local  circumstances 
and  exigencies.  In  the  survey  of  a  long 
and  hidden  valley,  affording  no  opportu- 
nity for  checks,  especial  care  must  be 
taken  to  preserve  the  integrity  of  the 
meander,  and  the  stations  must  be  espe- 
cially frequent;  but  in  a  survey  by  a 
direct  line  across  the  plain  two  or  three 
stations  a  day  may  be  sufficient.  In  a 
winding  path  up  a  mountain  side  a 
dozen  stations  may  be  necessary  if  there 
are  no  chances  for  checks;  but  if  the 
ends  of  the  trail,  at  the  top  and  bottom 
of  the  mountain,  can  be  located  by  the 
three-point  problem,  the  intermediate 
route  can  be  neglected,  being,  at  most, 
sketched  in  by  the  eye. 

There  are  two  considerations  to  govern 
the  occurrence  of  stations;  first,  to  pre- 
serve the  continued  accuracy  of  the  sur- 
vey, and  second,  to  note  the  local 
geographical  features  which  may  be 
encountered.  Fory  the  latter  purpose 


98 

stations  will  be  made  at  the  center  of 
every  village,  at  every  country-house  of 
importance,  at  the  crossing  and  diverg- 
ence of  streams,  roads  and  trails,  at  the 
opening  of  a  valley,  at  the  foot  and 
summit  of  a  mountain,  and  at  the 
many  other  geographical  vantage- 
grounds  which  the  practical  engineer 
will  know  how  to  select.  But  in  this,  as 
in  the  other  departments  of  the  survey, 
too  punctilious  zeal  may  defeat  its  own 
interests  by  causing  delay,  and  the  sur- 
veyor who  is  too  scrupulously  exact  in 
the  forenoon  may  have  to  virtually 
abandon  his  task  in  the  afternoon,  in 
order  to  reach  a  suitable  camping-ground 
by  night. 

SCOPE  OF  THE  MEANDER  SURVEY. 

The  zone  of  country  considered  from 
a  meander  line  may  extend  to  the 
farthest  visible  point,  as  a  series  of  sights 
upon  a  mountain  even  twenty-five  kilo- 
metres away  will  give  its  position  to  a 
close  approximation;  but  its  principal  in- 
tent is  the  preparation  of  a  narrow  route 


map,  the  areas  encompassed  by  whose 
windings  will  be  filled  in  from  the  topo- 
graphical stations.  Since,  from  its  nature 
and  narrow  scope,  it  is  fuller  and  takes 
cognizance  of  objects  more  minute  than 
can  be  noticed  in  the  other  systems,  in 
this  the  engineer  is  liable  to  a  charge  of 
partiality,  reproved  in  the  early  part  of 
this  article.  But  this  is  not  partiality  in 
one  field  at  the  cost  of  neglect  in 
another,  and  the  greater  excellence  of 
this  work  is  so  much  clear  gain.  More- 
over, since  the  meander  is  usually  by 
way  of  roads  of  frequent  travel,  and 
since  a  map  is  useful,  and  should  be  ex- 
cellent, exactly  in  proportion  to  the  num- 
ber of  people  who  are  guided  by  it,  it  is 
well  that  the  meander  plot  should  excel 
in  completeness  those  almost  inaccessible 
parts  which  will  never  be  seen  except  by 
the  hunter  or  bandit. 

MAKESHIFTS  IN  THE  SURVEY. 

In  a  forced  march  of  forty  kilometres 
or  more,  the  meteorologist  and  odometer 
recorder,  the  safe  carriage  of  whose  im- 


100 

plements  requires  a  slow  and  steady  gait, 
may  proceed  at  a  walk  after  taking  their 
readings  at  a  meander  station,  which  task 
will  occupy  them  but  a  few  minutes, 
while  the  surveyor  lingers  behind  to  make 
the  necessary  sketches  and  observations, 
and  then,  riding  at  gallop,  overtakes  his 
comrades  before  the  next  station  is 
reached.  Many  such  shifts  as  this  are 
known  to  the  practical  and  energetic 
geographer,  who  learns  to  emancipate 
himself  from  too  close  dependence  on  the 
text-books  of  surveying,  some  of  whose 
rules  are  very  common-place  and  pedan- 
tic, and  brings  into  play  his  powers  of 
ingenuity  and  invention,  to  adapt  himself 
to  the  peculiar  circumstances  by  which 
he  may  be  surrounded.  If  he  finds  him- 
self alone,  out  on  some  trip  of  hasty 
reconnoissance,  or  on  some  hunting  ex- 
cursion on  which  he  could  not  carry  both 
rifle  and  transit,  he  draws  from  his  watch 
pocket  an  aneroid,  and  from  his  saddle- 
bags a  pocket  compass  or  an  altazimuth, 
and  his  equipment  for  survey  is  com- 
plete; as  for  distances,  he  can  estimate 


101 

them,  or  determine  them  by  the  time 
they  take,  calculating  at  the  rate  of  five 
kilometres  an  hour,  or,  better  still,  by 
counting  the  steps  of  his  horse  and  allow- 
ing six  hundred  double  paces  for  a  kilo- 
metre. 

In  a  geological  survey  of  Brazil  very 
much  of  the  travel  and  exploration  is 
necessarily  done  by  water,  as  the  outcrop 
of  the  various  formations  is  most  favora- 
bly shown  upon  the  banks  of  the  rivers, 
along  which  there  is  frequently  no  passa- 
ble route  by  land.  Here  the  stadia  may 
be  used,  provided  there  are  two  or  more 
boats  in  the  party,  or,  in  the  less  import- 
ant instances,  the  methods  of  obtaining 
distances  by  estimation  or  by  time  would 
have  to  suffice.  In  either  case  the  sur- 
veyor should  lose  no  opportunity  to 
emerge  from  the  trough  of  the  stream, 
or  to  ascend  some  eminence,  and  insure 
his  position  by  observations  upon  three 
or  more  known  points.  Should  these  be 
wanting,  he  should  resort  to  the  sextant 
and  to  its  use  in  astronomical  determina- 
tions. 


102 

Since  the  attention  of  the  geologist  is 
in  great-  part  absorbed  in  the  duties  pe- 
culiar to  his  profession,  he  cannot  usually 
carry  any  but  the  lightest  and  most  con- 
venient implements  of  survey,  and  since 
these  are  amply  sufficient  for  his  geologi- 
cal notes  of  dip,  strike,  trend,  etc.,  it  is  a 
matter  of  expediency  to  make  them  an- 
swer for  his  geographical  work  as  well. 
With  the  engineer,  however,  there  rarely 
comes  a  necessity  for  being  separated 
from  his  portable  transit,  which  admits 
of  being  firmly  set  on  its  tripod,  and  from 
which  angles,  either  horizontal  or  verti- 
cal, may  be  accurately  read  to  the  near- 
est minute.  And  in  the  general  geo- 
graphical plan  it  is  wise  to  deprecate  as 
far  as  possible  the  employment  of  unreli- 
able pocket  instruments,  or  of  the  devices 
for  learning  distances  that  have  been  de- 
tailed above.  Since  nothing  is  to  be 
gained  in  time  by  their  use,  and  very 
much  may  be  lost  in  accuracy,  the  engi- 
neer should  teach  himself  to  consider  that 
any  method  less  complete  than  that  of 
the  portable  transit  and  odometer  is  but 


103 

a  temporary  expedient  and  makeshift, 
serving  an  excellent  purpose  when  all 
other  means  fail,  but  not  to  be  relied 
upon  as  a  permanent  constituent  of  the 
survey. 

CO-OPERATION     OF     THE      TRIANGULATION 
AND    MEANDER. 

While  the  meander  survey  is  an  ex- 
cellent apprenticeship  for  the  young  en- 
gineer, it  should  not  be  despised,  as  an 
occupation,  by  even  the  director  of  the 
triangulation.  Humble  as  it  is,  it  per- 
forms a  task  in  the  geographical  plan 
which  no  system  of  triangulation  can  be 
relied  upon  to  perform  in  a  rapid  work 
of  this  nature.  It  enables  the  survey  to 
reach  any  point,  however  remote  and  se- 
cluded, and  to  determine  its  positions;  it 
makes  the  map  complete  in  all  of  the 
details  which  are  so  useful  to  the  trav- 
eler; and  as  an  agent  in  what  we  may 
call  the  practical  or  economical  branch 
of  geography  it  is  without  an  equal. 

It  is  dependent  upon  the  triangulation, 
it  is  true,  but  then  the  dependence  is 


104 

mutual.  The  full  benefit  of  either  can 
only  be  secured  through  the  co-opera- 
tion of  the  two.  As  without  the  trian- 
gulation  the  map  is  unreliable,  so  with- 
out the  meander  it  is  incomplete.  To 
use  a  homely  illustration,  the  triangula- 
tion  may  be  compared  to  the  framework 
of  the  dwelling,  and  the  meander  to  the 
intermediate  filling  of  wall  or  other  sub- 
stance which  makes  the  house  habitable, 
and  is  a  shelter  to  the  inmates.  This 
frame,  if  its  lines  are  true  and  its  angles 
correct,  is  a  beautiful  thing  for  the  arti- 
san to  contemplate,  but  without  its  com- 
pletion of  walls  and  furniture,  it  is  of  no 
real  benefit  to  the  world.  In  the  same 
manner  a  bare  triangulation  scheme  may 
be  an  interesting  study  to  the  geographer 
himself,  but  to  the  traveling  public  and 
the  people  at  large,  it  possesses  neither 
interest  nor  value.  On  the  other  hand, 
as  the  frame  of  the  house  is  an  absolute 
necessity  to  it,  securing  and  sustaining  it 
in  its  proper  proportions,  so  is  the  trian- 
gulation the  rigid  frame  work  of  the 
map  and  the  skeleton  to  which  the  use- 
ful data  of  the  meander  are  attached. 


105 

CHECKS    BY   THE    THREE-POINT     PROBLEM. 

Since  the  meander  is  from  its  very 
nature  so  hasty  and  loose,  the  system  of 
frequent  checks  can  alone  make  it  relia- 
ble, and  at  intervals  of  every  few  kilo- 
metres, and  especially  at  the  crossing*  of 
divides  and  other  eminences  from  which 
there  is  a  broad  scope  of  country  visible, 
connection  should  be  made  with  the 
triangulation.  Each  of  these  stations 
then  becomes  a  new  initial  point,  at 
which  the  survey  begins  afresh  and  the 
error  again  begins  to  accumulate. 

This  rectification  is  accomplished  by 
the  use  of  the  three-point  problem,  a 
geodetic  determination  which,  as  a 
means  of  locating  topographical  stations, 
and  as  a  connecting  link  between  the 
meander  and  the  triangulation,  is  of  the 
highest  importance  in  geographical  sur- 
veying. Having  three  triangulation  sta- 
tions in  sight,  and  favorably  situated,  it 
is  possible  for  the  observer  to  determine 
his  position  in  a  few  minutes  of  time 
and  by  the  simple  operation  of  reading 
the  two  angles  included  by  those  three 


106 

stations.  From  these  and  the  data  per- 
tinent to  the  triangulation  stations  he 
can  compute  his  distance  from  them,  and 
hence  his  present  latitude  and  longitude. 
Or,  plotting  these  angles  from  any  cen- 
ter on  a  piece  of  tracing  cloth,  he  can 
lay  this  upon  the  projected  map  and 
swing  it  around  until  each  of  the  three 
plotted  rays  covers  its  proper  triangula- 
tion point,  when  this  center  will  indicate 
the  position  of  the  three-point  station,  as 
it  is  called.  For  this  graphic  determina- 
tion not  only  three  points,  but  four,  and 
even  more,  if  they  are  visible,  should  be 
observed,  as  a  greater  number  facilitate 
the  operation  and  insure  the  accuracy 
of  the  result. 

This  method  of  trilinear  determinations 
cannot  be  introduced  too  often.  A 
three- point  station  in  the  streets  of  a 
settlement,  at  the  forks  of  a  road,  or  at 
the  end  of  a  mountain  range,  will  locate 
these  important  places,  and  in  camp, 
even  in  the  center  of  a  broad  and  vacant 
plain,  there  is  no  more  profitable  man- 
ner in  which  the  engineer  can  spend  his 


107 

leisure  time,  before  or  after  dinner,  than 
by  making  a  three-point  station  there 
and  determining  his  position.  Every 
camp  thus  fixed  is  a  new  and  reliable 
origin  at  which  the  meander  of  the  next 
morning  will  begin. 

A      SURVEY     BY      THREE-POINT      STATIONS 
ALONE. 

In  some  cases  a  successful  meander 
may  be  carried  on  by  three-point  sta- 
tions alone,  when  all  other  means  would 
fail.  Take,  for  instance,  the  rugged 
shores  of  a  lake  or  bay,  which  are  inac- 
cessible except  to  a  man  on  foot  or  in  a 
boat.  In  the  mountains  on  the  other 
side  of  the  water  a  series  of  triangula- 
tion  stations  stand  up  in  full  view.  By 
means  of  these  the  engineer,  working 
his  way,  transit  in  hand,  from  bay  to 
bay,  and  from  point  to  point,  along  the 
water's  edge,  makes  three-point  stations 
at  all  prominent  changes  of  curvature, 
and,  sketching  in  the  intermediate  shore, 
he  determines  its  line  by  tangents  and 
intersections,  and  thus  secures  a  good 


108 

survey  of  the  coast.  If  there  are  islands 
out  in  the  water  they  may  be  surveyed 
in  the  same  way. 

If  the  engineer  was  confronted  with  a 
piece  of  geography  like  the  bay  and 
islands  of  Rio  de  Janeiro,  and  if  there 
were  no  roads  along  the  beach  to  make 
direct  linear  measurements  feasible,  he 
could  extend  his  triangulation  to  include 
all  of  the  prominent  peaks  in  the  vicinity, 
and  then,  by  means  of  three-point  sta- 
tions, he  could  rapidly  trace  in  the  shore- 
line. As  the  surroundings  of  Rio  are  so 
broken  and  irregular,  the  triangulation 
points  could  be  made  so  numerous  that 
it  would  be  difficult  to  find  a  spot  on  the 
beach  of  mainland  or  island  so  secluded 
that  some  three  of  these  stations  would 
not  be  visible  from  there. 

THE  MEANDER  PLOT. 

Every  three-point  station,  as  well  as 
every  other  meander  station,  should  par- 
take more  or  less  of  the  nature  of  a  regu- 
lar topographical  station;  that  is,  contour 
sketches  should  be  kept  constantly  on 


109 

the  plotted  page  as  it  progresses,  and  a 
continuous  panorama  of  profile  views, 
drawn  in  a  separate  portion  of  the  book, 
should  accompany  the  survey,  so  that, 
as  some  geographical  features  are  left  in 
the  rear,  others  may  be  introduced  in 
advance. 

As  from  one  topographical  station  to 
its  neighbor,  so  every  distance  from  one 
meander  station  to  the  next  should  be 
considered  a  base  to  be  used  in  the  loca- 
tion of  points  useful  in  the  structure  of 
the  map.  The  longer  this  base,  the  more 
distant  may  be  the  range  of  these  views. 
In  case  several  meander  stations  inter- 
vene between  one  observation  and  the 
following,  this  total  intermediate  dis- 
tance becomes  what  is  called  a  broken 
base,  but  it  is  none  the  less  useful  for  all 
of  that.  The  above  considerations  will 
influence  the  engineer  in  his  choice  of 
stations,  which  will  always  be  situated  in 
such  positions  as  may  offer  the  best  ad- 
vantages for  the  accumulation  of  what- 
ever information  he  most  needs. 


110 

THE     DECLINATION    OF    THE    COMPASS 
NEEDLE. 

The  variation  of  the  compass  needle, 
or,  more  properly,  its  declination,  will  be 
carefully  watched  throughout  the  sur- 
vey, and  determinations  of  its  angle  will 
be  made  from  time  to  time;  these  will  be 
more  than  usually  frequent  wherever 
there  is  suspicion  of  some  attraction  im- 
mediately local,  arising  from  the  presence 
of  magnetite  or  other  ore  of  iron,  basaltic 
rock,  or  other  disturbing  influence.  These 
determinations  are  important,  not  only 
in  the  reduction  of  the  meander  notes 
taken  in  this  vicinity,  but  also  for  the 
practical  use,  both  present  and  future, 
of  the  country  at  large.  In  addition,  their 
results  will  aid  the  general  cause  of  sci- 
ence in  its  investigation  of  the  laws  of 
terrestrial  magnetism,  and  in  tracing  the 
course  of  isogonic  lines  around  the  world. 

At  every  triangulation,  topographical, 
and  three-point  station,  the  observer 
will  note  the  direction  of  magnetic 
north,  as  indicated  by  the  pointing  of 
the  compass  needle.  If  his  instrument 


Ill 

has  a  double  movement  in  azimuth,  as 
all  should  have,  it  is  well,  for  the  sake  of 
convenience,  to  first  set  the  zero  of  the 
graduated  limb  upon  the  same  point  of 
the  vernier  plate,  by  the  upper  motion, 
and  then,  by  means  of  the  lower  move- 
ment, bring  the  north  end  of  the  needle 
to  the  zero  of  its  circle.  His  initial 
entry  in  his  note-book  will  then  be 
"  Magnetic  North,  0°  00'  00"."  This 
direction  of  the  telescope  being  referred 
to  some  line  proceeding  from  here, 
whose  true  azimuth  will  be  found  by 
subsequent  computation,  the  magnetic 
azimuth  or  declination  of  the  needle  at 
that  place  will  be  determined;  it  will 
simply  be  the  difference  between  the  true 
azimuth  of  the  line,  reckoned  from  the 
north  point  of  the  horizon,  and  its  ap- 
parent azimuth,  or  the  vernier  reading 
which  he  enters  in  his  notes. 

BY    DIRECT   ASTRONOMICAL     OBSERVATION. 

The  declination  of  the  needle  will  also 
be  determined  directly  by  astronomical 
observation  in  the  evening  at  camp.  For 


112 

this  purpose  the  engineer  will  select  such 
nights,  clear  and  still,  as  may  appear  to 
him  most  favorable,  and  such  camping 
places  as  may  most  urgently  require  this 
information.  A  star  as  near  as  possible 
to  the  pole  will  be  chosen,  as,  from  its 
greater  declination,  an  error  in  the  lati- 
tude of  the  observer's  place,  and,  from 
its  slower  motion,  an  error  in  the  time 
of  the  observation,  will  result  in  less 
serious  errors  in  the  azimuth;  and  the 
smaller  the  polar  distance  of  the  star,  the 
more  convenient  will  be  the  observation 
and  the  computations  which  follow,  and 
the  more  exact  is  the  result  likely  to  be. 
In  the  northern  hemisphere  a  Ursce  Mi- 
noris,  or  Polaris,  is  almost  always  used, 
as  it  is  at  present  only  about  1°  20'  from 
the  pole,  and  it  possesses  the  additional 
advantage  of  a  brilliancy  of  the  second 
order.  But  south  of  the  equator  there 
are  no  available  stars  so  favorably  situ- 
ated as  this.  The  most  southern  one  of 
any  considerable  size  is  ft  Hydri,  of  the 
third  magnitude,  whose  polar  distance  is 
a  little  more  than  twelve  degrees. 


113 

This  would  have  to  be  accepted  in  a 
survey  of  this  nature  in  preference  to 
any  of  the  less  brilliant  stars  of  greater 
declination,  as  the  observations  would 
have  to  be  made  frequently  by  engineers 
of  little  astronomical  experience,  and 
with  instruments  not  especially  adapted 
to  this  kind  of  work.  Indeed,  it  might 
be  necessary  at  times  to  use  the  small 
meander  transit  for  that  purpose;  arid  it 
is  seldom  that  the  telescopes  of  even  the 
theodolites  for  triangulation,  as  now  con- 
structed, are  provided  with  the  hollow 
rotation  axis  requisite  for  a  proper  illu- 
mination of  the  diaphragm,  without 
which  it  is  difficult  to  see  both  cross- 
hair and  star,  unless  the  latter  is  of  con- 
spicuous magnitude. 

Knowing,  at  least  approximately,  the 
latitude  of  the  place,  and  also  the  decli- 
nation of  the  star  and  its  hour  angle  at 
the  time  of  observation,  its  azimuth 
angle  from  the  south  point  can  be  com- 
puted. But  as  the  hour  angle  depends 
upon  the  local  time  at  that  place,  and 
there  is  great  room  for  error  there,  the 


114 

observer,  unless  he  has  full  confidence  in 
his  ability  to  make  an  accurate  time-de- 
termination, should  find  the  approximate 
minute  of  the  star's  greatest  elongation, 
and  follow  it  with  the  transit  thread 
until  it  reaches  the  dead  point  in  its 
azimuth  motion,  where  it  seems  to  stop 
a  few  moments  between  its  advance  and 
retrogression.  Then,  being  at  its 
greatest  elongation,  the  sine  of  its  azi. 
muth  angle  is  equal  to  the  cosine  of  its 
declination  divided  by  the  cosine  of  the 
latitude  of  the  place. 

Should  the  star  0  Hydri  not  arrive  at 
its  east  or  west  point  at  a  convenient 
hour,  as  at  certain  seasons  of  the  year  it 
will  not,  the  star  Canopus,  differing  in 
right  ascension  about  six  hours,  or  a 
Trianguli  Australis,  of  about  sixteen 
hours  greater  right  ascension,  may  be 
employed.  These  are  respectively  of  the 
first  and  second  magnitude,  and  hence 
are  very  well  adapted  to  this  purpose, 
but,  owing  to  their  greater  polar  dis- 
tances, it  would  be  necessary,  in  their  use, 
for  the  observer  to  be  especially  sure  of 
the  correctness  of  his  latitude. 


115 

The  sun  is  not  usually  available  for 
determinations  of  azimuth  or  time,  as 
the  engineer  is  generally  upon  the  march 
throughout  the  day.  The  use  of  a  star, 
however,  admits  of  greater  precision  in 
the  observations,  while  the  resulting 
computations  are  less  complicated,  and, 
in  the  case  of  an  azimuth  determination, 
a  south  star  is  doubly  convenient  from 
the  fact  that  its  two  daily  elongations 
always  come  above  the  horizon,  and 
whichever  one  occurs  most  opportunely 
may  be  used;  or  it  may  be  possible  at 
times  to  observe  both,  in  which  case  it 
becomes  unnecessary  for  the  engineer  to 
know  his  latitude.  The  same  difficulty 
of  latitude,  may  also  be  avoided  by  the 
method  of  equal  altitudes  of  a  star,  taken 
at  several  hours  before  and  after  its 
meridian  passage;  the  middle  point  be- 
tween the  two  corresponding  azimuths 
will  be  upon  the  meridian. 

THE     METEOROLOGIST     AND     HIS     INSTRU- 
MENTS. 

In  all  of  his  travels  the  meteorologist 
will  be  the  constant  companion  of  the 


116 

engineer,  so  as  to  be  prepared  to  take 
observations  at  any  point  that  the  latter 
may  designate.  At  the  beginning  of  the 
field  season  he  will  be  furnished  with,  at 
least,  two  complete  sets  of  meteorological 
instruments,  to  be  carried  by  himself  and 
by  others  who  may  be  appointed  to  as- 
sist him.  Each  set  will  be  composed  of 
a  cistern  barometer,  an  aneroid,  maxi- 
mum and  minimum  thermometers,  pocket 
thermometers,  and  a  psychrometer,  con- 
sisting of  two  similar  thermometers,  one 
with  its  bulb  capable  of  being  moistened 
by  the  capillary  attraction  of  a  loose  cord 
of  cotton  filaments  leading  to  it  from  a 
cup  of  water,  and  the  other  dry,  as  in  the 
ordinary  instrument. 

Prior  to  taking  the  field  he  will  com- 
pare these  barometers  by  a  series  of 
readings  extending  through  several  days, 
with  some  standard  barometer  whose  er- 
ror is  known,  in  order  to  obtain  the  in- 
strumental errors  of  the  instruments  at 
hand.  Throughout  the  season,  also,  he 
will  lose  no  opportunity  for  comparisons 
with  any  reliable  barometers  that  may 


117 

be  encountered,  as  well  as  for  frequent 
comparisons  between  these  two.  In  this 
manner  the  time  of  any  possible  disloca- 
tion of  the  scale,  or  other  source  of  error, 
will  be  determined. 

As  in  the  rough  and  rapid  travel  of  a 
geographical  survey,  there  is  great  lia- 
bility to  break  the  fragile  glass  tube 
which  contains  the  heavy  mercurial  col- 
umn, an  extra  supply  of  barometer  tubes 
and  mercury  should  be  transported  with 
the  party,  and  also  an  assortment  of 
tools  and  material  for  the  filling,  boiling, 
and  fitting  of  a  fresh  tube.  This  is  a 
delicate  and  difficult  task,  but  it  is  one 
in  which  every  meteorologist  should  be 
proficient.  As  full  instructions  for  the 
use  and  repair  of  meteorological  instru- 
ments have  already  been  prepared  by 
the  Commission,  it  is  needless  to  repeat 
them  here. 

METEOROLOGICAL    OBSERVATIONS. 

At  every  station  of  the  survey,  the 
meteorologist  will  read  from  his  instru- 
ments the  data  from  which  the  elevation 


118 

of  that  point  may  be  subsequently  com- 
puted. Nothing  more  is  then  needed 
for  the  precise  determination  of  that 
station's  position.  The  engineer  has  fixed 
it  in  latitude  and  longitude;  the  mete- 
orologist, in  its  altitude  above  sea-level. 
The  meteorological  data  will  be  more  or 
less  comprehensive  and  will  be  read  from 
instruments  more  or  less  reliable,  accord- 
ing to  the  geographical  importance  of 
the  place  at  which  they  are  taken.  The 
more  frequent  the  readings,  and  the 
more  prolonged  the  series,  the  more 
trustworthy  will  the  resulting  mean  be, 
and  the  less  liable  to  be  materially 
affected  by  errors  of  observation,  and 
by  those  erratic  fluctuations  to  which  the 
barometer  is  subject,  owing  to  the  con- 
stantly varying  atmospheric  currents  and 
other  disturbing  physical  conditions  to 
which  it  is  exposed,  and  whose  effect 
cannot  be  entirely  eliminated  by  any 
formulas  that  it  is  possible  to  devise. 

Beginning  at  the  point  of  outfit, 
which,  on  account  of  the  work  of  pre- 
paration and  the  measurement  of  the 


119 

base-line,  may  be  occupied  some  weeks 
or  a  month,  hourly  readings  will  be  taken 
throughout  the  day  and  night  for  as 
long  a  time  as  possible.  The  cistern 
barometers  will  be  read,  as  the  height  of 
the  mercurial  column  is  the  basis  upon 
which  all  barometrical  determinations 
rest.  The  attached  thermometer  will 
be  read,  to  learn  the  temperature  of  the 
mercury,  and  hence  what  correction 
must  be  applied  to  reduce  it  to  the 
freezing  point,  at  which  all  barometrical 
heights  are  compared.  The  isolated 
thermometer  will  give  the  temperature 
of  the  surrounding  atmosphere,  to  be 
used  in  determining  the  mean  tempera- 
ture of  the  stratum  of  air  intermediate 
between  this  and  the  reference  station. 
And  the  psychrometer  will  reveal  the 
amount  of  aqueous  vapor  in  the  atmos- 
phere, and  the  influence  of  its  pressure 
upon  the  height  of  the  column  of  mercu- 
ry. In  addition  to  these,  note  will  also 
be  taken  of  the  direction  and  force  of  the 
wind,  the  condition  of  the  sky,  the  proxi- 
mity of  storms,  and  other  atmospherical 


120 

phenomena,  as  this  information  may 
give  the  key  to  some  abnormal  baro- 
metric oscillation  which  would  otherwise 
have  to  remain  unexplained. 

HORARY  AND   ABNORMAL    OSCILLATIONS. 

The  hourly  observations  will  be  con- 
tinued throughout  the  day  and  night  for 
the  purpose  of  determining  the  amount 
of  the  horary  oscillation  at  that  place. 
This  horary  oscillation  is  a  somewhat 
regular  rise  and  fall  of  the  barometer, 
occupying  a  period  of  twenty-four  hours. 
The  range  of  this  fluctuation  in  some 
parts  of  the  world  is  so  great,  that  its 
effect  upon  the  mercurial  column  may 
equal  that  which  would  be  produced  by 
a  change  of  fifty  meters  in  altitude.  It 
is  such  that,  if  the  successive  heights  of 
the  column  be  represented  graphically 
by  a  curve,  this  curve  will  show  two 
daily  maxima  and  minima,  occurring  at 
intervals  of  about  six  hours,  the  morning 
maximum  being  attained  at  about  ten 
o'clock  A.  M.  This  horary  curve,  as  it 
is  called,  varies  with  the  latitude,  alti- 


121 

tade,  and  climate  of  a  place,  as  well  as 
with  the  different  portions  of  the  year. 
The  value  of  the  horary  variation  for 
any  hour  of  the  day  is  revealed  by  a 
study  of  the  prolonged  series  of  observa- 
tions at  that  place,  and  may  be  assumed 
to  be  the  same  for  all  observations  taken 
in  the  vicinity  of  that  station  and  in  the 
same  season  of  the  year. 

The  barometer  is  also  influenced  by 
the  abnormal  oscillation,  apparently  re- 
sulting from  the  progress  of  great  atmos- 
pheric waves  across  the  country,  affect- 
ing the  mercurial  column  by  a  gradual 
rise  of  several  days,  followed  by  a  period 
of  subsidence  of  about  an  equal  duration. 
The  effect  of  this  disturbance  can  be 
eliminated,  approximately,  by  taking  the 
difference  of  the  barometric  readings  at 
the  beginning  and  ending  of  any  one  day 
of  its  rise  or  fall,  and  considering  this  as 
its  amount  for  that  twenty  four  hours,  a 
proportional  part  of  which  will  be  its 
value  for  one  hour. 


122 

DETERMINATION    OF    HEIGHTS. 

To  obtain  the  altitude  of  the  first 
station  of  the  survey,  a  mean  of  the  cor- 
rected heights  of  the  mercurial  column 
is  compared  with  a  corresponding  mean 
of  the  same  hours  of  the  same  days  at 
some  permanent  station,  whose  elevation 
above  the  sea  is  definitely  known,  as,  for 
instance,  the  Imperial  Observatory  at 
Rio  de  Janeiro.  This,  by  a  process  of 
computation,  gives  their  difference  of 
altitude,  and  hence  the  total  elevation  of 
the  point  in  question. 

Now,  making  this  point  of  outfit  a 
reference  station,  at  which  an  observer  is 
left  with  meteorological  instruments  to 
be  read  at  stated  intervals  throughout  the 
day,  the  party  takes  the  field,  and  the 
traveling  meteorologist  reads  a  series  of 
barometrical  and  other  observations  at 
the  first  camp  and  at  all  others  to  which 
they  may  come  during  the  season. 
These  will  be  compared,  as  before,  with 
synchronous*  observations  at  the  refer- 

*  It  is  well  to  distinguish  between  the  meanings,  as  now 
understood,  of  the  two  words  "  synchronous  "  and  "  sim- 


123 

ence  station,  and  the  differences  of  alti- 
tude will  be  calculated.  At  every  topo- 
graphical station,  and  station  of  import- 
ance along  the  meander  survey,  such  as 
villages,  f azendas,  mines,  mountain  passes, 
divides,  etc.,  and  at  all  other  points  that 
may  be  designated  by  the  engineer,  the 
meteorologist  will  read  the  cistern  baro- 
meter, the  watch,  the  thermometer,  and 
the  psychrometer,  and,  for  the  purposes 
of  comparison,  the  aneroid  barometer  as 
well.  These  isolated  observations  will 
also  be  referred  to  the  main  barometrical 
station  at  a  distance. 

But,  on  the  occasion  of  the  ascent  of 
a  mountain  peak  from  a  fixed  camp,  bet- 
ter results  will  be  obtained  by  consider- 


ultaneous."  The  term  "  simultaneous  "  is  applied  to  ob- 
servations which  are  made  at  the  same  absolute  instant 
of  time,  as,  for  instance,  upon  the  occultations  and 
eclipses  of  the  heavenly  bodies.  Synchronous  observa- 
tions are  taken  at  the  same  hour  of  the  day,  local  time, 
irrespective  of  the  difference  of  longitude  between  the 
two  stations.  Therefore,  observations  can  be  both  sim- 
ultaneous and  synchronous  only  when  the  observers  are 
upon  the  same  meridian.  The  word  "  simultaneous " 
belongs  especially  to  the  province  of  astronomy,  whilst 
"  synchronous  "  is  most  frequently  used  in  connection 
with  the  phenomena  of  physical  geography. 


124 

ing  the  camp  a  reference  station  in  the 
determination  of  the  altitude  of  the 
mountain.  This  ascent  will  necessitate 
the  occupancy  of  the  neighboring  camp 
for  two  nights  and  a  day  at  least,  and 
perhaps  longer,  while  the  peak  may  be 
occupied  only  a  portion  of  a  day,  during 
which  time,  however,  there  will  be  cor- 
responding hourly  observations  at  camp 
and  mountain-top.  Hence  the  altitude 
of  the  mountain  will  be  most  truthfully 
ascertained  by  referring  it,  by  these  syn- 
chronous observations,  to  the  camp,  and 
then  the  camp,  in  a  similar  manner,  to 
the  distant  reference  station. 

HORARY     CURVES     AND     REFERENCE     STA- 
TIONS. 

Whenever  the  party,  or  a  portion  of 
it,  remains  stationary  in  camp  for  a  few 
days  at  a  time,  hourly  observations  day 
and  night  will  be  taken  to  determine  the 
horary  curve  at  that  place;  the  longer 
the  series,  the  better  will  be  the  result. 
Since  the  horary  variations  are  constantly 
changing  with  altitude,  country  and  cli- 


125 

mate,  it  is  important  to  have  as  frequent 
determinations  of  them  as  can  practicably 
be  made,  so  that  no  very  great  distance 
may  intervene  between  the  place  where 
a  table  of  horary  corrections  is  construct- 
ed and  the  place  where  it  is  used. 

For  a  similar  reason  it  may  be  deemed 
necessary  to  establish  and  sustain  a  sec- 
ond meteorological  reference  station,  if 
the  field  of  the  season's  survey  should  be 
a  wide  one,  or  if  it  should  vary  greatly 
in  the  atmospherical  condition  of  differ- 
ent portions  of  its  area.  No  comprehen- 
sive rule  can  be  given  to  govern  the  num- 
ber of  these  reference  stations;  all  must 
depend  upon  the  judgment  of  the  direc- 
tor of  the  survey,  and  the  resources  at 
his  command.  In  general,  the  farther 
the  place  of  an  observation  from  its 
reference  station,  the  less  reliable  will  be 
its  result.  But,  as  an  exception,  let  us 
take  the  example  of  a  broad  inland  plain, 
separated  from  the  sea  and  its  influences 
by  a  wall  of  mountains,  within  which, 
upon  the  plain,  the  reference  station  is 
situated.  In  this  case  it  may  be  more 


326 

justifiable  to  refer  to  this  station  a  point 
on  the  plain,  five  hundred  kilometres  dis- 
tant, than  one  just  over  the  mountains, 
only  one  hundred  kilometres  away.  This 
is  owing  to  the  widely  different  climatic 
circumstances  of  inland  and  sea-coast, 
resulting  in  meteorological  conditions  so 
dissimilar  that  equal  amounts  of  pressure 
cannot  be  relied  upon  as  an  indication  of 
equal  thickness  of  the  atmospheric  enve- 
lope. 

THE  ANEROID  BAROMETER. 

At  the  many  stations  of  the  meander 
survey  that  are  comparatively  unimport- 
ant, and  that  are  occupied  for  a  few  min- 
utes only,  it  will  suffice  for  the  meteoro- 
logist to  read  only  his  aneroid,  watch, 
and  thermometer.  Although  the  aneroid 
is  not  a  reliable  instrument,  yet  it  serves 
an  excellent  purpose  where  rapid  and  ap- 
proximate work  is  sufficient.  Since  its 
principal  use  is  in  obtaining  profiles  of 
the  meander  routes,  which  will  enable 
the  engineer  to  properly  distribute  the 
contour  lines  upon  his  map,  and  since, 


127 

farther,  the  error  of  an  aneroid  will  rare- 
ly exceed  the  vertical  distance  between 
two  of  these  contours,  the  resulting  inac- 
curacy upon  the  plot  will  be  quite  inap- 
preciable. 

The  aneroid  is  to  the  cistern  barometer 
what  the  meander  is  to  the  triangulation, 
that  is,  a  means  of  filling  in,  which, 
while  costing  but  little  extra  effort, 
is  productive  of  very  valuable  results. 
The  engineer  who  rejects  the  meander 
and  the  aneroid,  because  they  are  not 
rigidly  exact  in  their  functions,  will  find 
himself  reduced  to  the  necessity  of 
tracing  in  the  roads  and  streams  of  his 
map,  locating  many  of  the  villages,  cross- 
roads, etc.,  and  drawing  in  the  contours 
from  his  judgment  and  memory  alone; 
and  it  is  safe  to  say  that  the  conjectures 
of  the  most  able  and  trained  topographi- 
cal intellect  are  by  far  less  reliable  than 
the  figures  of  those  humble  instruments, 
the  aneroid  and  odometer,  when  judi- 
ciously used. 

At  every  camp  the  aneroids  are  com- 
pared with  the  cistern  barometer,  their 


128 

scales  are  adjusted  in  compensation  for 
any  error  that  may  have  crept  in,  and 
the  vertical  element  of  the  survey  starts 
from  a  new  and  true  datum  plane  when 
the  march  is  resumed.  At  the  end  of 
the  day's  journey,  also,  they  are  imme- 
diately compared  again,  and  the  error 
accumulated  throughout  the  day  is 
noted,  and,  by  a  process  of  distribution 
along  the  day's  profile,  may  be  reduced 
to  a  minimum.  Before  and  after  every 
side  trip,  reconnoissance,  or  ascent  of 
mountain,  the  aneroid  is  compared  with 
the  mercurial  barometer,  and  thus,  by  a 
continual  and  careful  watch  over  it,  it 
may  be  relied  upon  to  give  results  not 
seriously  in  error.  But  if  left  to  itself 
and  unchecked  for  any  great  length  of 
time,  or  for  any  great  distance  of  journey, 
or  great  change  in  altitude,  this  fickle  in- 
strument may  continue  to  go  astray,  by 
a  shifting  of  its  scale,  exhaustion  of  its 
spring,  or  from  other  causes,  until  its 
readings  are  hundreds  of  metres  too 
high  or  too  low.  Even  then,  however, 
it  may  be  of  use  to  the  geographer  in 


129 

drawing  in  the  relief  of  the  country,  as 
the  discrepancy  is  usually  of  gradual 
growth,  and  the  relative  altitudes  during 
the  progress  of  the  survey,  as,  for  in- 
stance, the  height  of  a  bluff  above  the 
neighboring  valley,  are  sufficiently  exact 
to  be  of  much  assistance  to  him  in  his 
plotting. 

BAROMETRICAL    RESULTS. 

As  to  the  reliability  of  altitudes  de- 
termined by  the  cistern  barometer,  evi- 
dences and  opinions  differ,  but  those  per- 
sons who  are  most  thoroughly  informed 
are  generally  the  most  lenient  in  their 
acceptation  of  results.  Colonel  Wil- 
liamson, of  the  United  States  Army,  who 
has  probably  given  more  intelligent 
study  to  the  barometer  than  any  other 
man,  has  compiled  a  table  of  the  maxi- 
mum errors  which  occur  in  numerous 
series  of  observations  taken  both  in  North 
America  and  Europe.  Among  these  are 
many  that  exceed  fifty  meters  in  amount, 
and  he  assumes  that  the  barometer  under 
similar  circumstances  will  be  liable  to 


130 

equal  errors  elsewhere.    These,  however, 
are  not  to  be  considered  as  representing 
the   probable   error  of  barometrical  re- 
sults; they  are  rather  the  extreme  limits 
of  probable  error,  and  may  be  taken  as 
the  error  to  which  the  barometer  is  liable 
under  certain  rare  and  very  unfavorable 
conditions.     While  exact  truth  concern- 
ing   altitudes   is    something   which    no 
barometer  can  be  expected  to  tell,  and 
while  it  is  never  safe  to  guarantee  the 
accuracy  of  such  a  determination,  even 
within   many    meters,    yet   when    baro- 
metrical work  is  prosecuted  judiciously 
and  systematically,  as  it  would  be  in  this 
survey,  and  based  upon  formulas  which 
represent  the  latest  and  most  complete 
knowledge  of  meteorology,  its  tendency 
is  to  give  results  that  are  seldom  more 
than  a  few  meters  wrong. 

It  is  often  difficult  for  the  popular 
mind  to  comprehend  how  an  error  of 
meters  may  be  inevitable  in  some  of  the 
processes  of  barometric  hypsometry. 
Since  the  scale  of  a  barometer  may  be 
read  to  a  thousandth  of  an  inch,  and  that 


131 

amount  of  variation  is  supposed  to  cor- 
respond to  a  change  of  one  foot  in  alti- 
tude, it  would  naturally  be  thought 
possible  to  determine  the  elevation  of  a 
place  to  the  nearest  foot.  But  this  diffi- 
culty will  be  better  understood  when  it 
is  remembered  that  the  barometrical 
measurement  of  the  difference  of  altitude 
between  two  places  depends  upon  the 
determination  of  the  weights  of  a  column 
of  atmosphere  at  each  of  these  stations; 
that  this  atmosphere  is  in  a  state  of  con- 
stant change  and  perturbation,  its  press- 
ure being  modified  by  variations  of  heat 
and  cold,  storm  and  calm,  and  the 
absence  and  presence  of  moisture  through- 
out different  portions  of  its  extent;  and 
that,  while  some  of  these  conditions  are 
quite  unknown  to  the  observer,  those 
that  are  apparent  to  him  can  be  but  in- 
completely compensated  for.  There- 
fore, since  barometric  hypsometry  is  not 
one  of  the  exact  sciences,  but  is  affected 
by  every  change  in  the  wind  and 
weather,  any  determination  of  altitude 
that  is  true  within  a  meter  is  as  much 


132 

a  source  of  surprise  as  of  gratification  to 
the  meteorologist,  who  will  be  obliged 
to  confess  that  this  closeness  could 
scarcely  be  possible  without  some  coin- 
cidence and  accidental  equilibrium  in 
the  disturbing  influences  to  which  the 
barometer  is  subject. 

DIFFICULTIES     IN    BAROMETRIC 
HYPSOMETRY. 

At  times  men  of  little  experience  may 
have  to  be  accepted  as  meteorologists. 
They  work,  perhaps,  under  the  embar- 
rassments of  exposure,  fatigue,  and  a 
lack  of  appreciation  of  the  responsibilities 
that  rest  upon  them.  It  may  be  long 
before  they  can  be  taught  to  regard 
those  niceties  of  barometrical  work  with- 
out which  it  cannot  be  truly  successful; 
although  there  is  but  little  hope  of 
determining  an  altitude  to  the  single 
foot,  yet  they  have  to  learn  that  this  is 
no  reason  for  neglecting  that  thousandth 
of  an  inch  which  corresponds  to  a  foot. 
Their  instruments  may  be  out  of  order, 
owing  to  the  hardships  of  travel  to  which 


133 

they  are  exposed;  the  readings  may  have 
to  be  referred  to  a  distant  station  of  very 
dissimilar  physical  surroundings;  or  they 
may  have  been  taken  upon  the  top  of  a 
lofty  mountain,  in  a  belt  of  the  atmos- 
phere with  meteorological  phenomena 
quite  different  from  those  properties  of 
the  lower  strata  of  the  air,  for  which 
our  formulas  were  framed. 

These  are  some  of  the  sources  of  error 
which  may  have  conspired  to  vitiate 
those  results  which  are  fifty  meters  or 
more  at  fault.  In  Brazil,  however,  it  is 
hardly  necessary  to  anticipate  discrepan- 
cies so  great  as  this,  since  it  is  a  country 
in  which  no  very  great  change  of  alti- 
tude is  possible,  violent  and  phenomenal 
storms  are  not  frequent,  and  the  atmos- 
phere is  of  comparatively  steady  tem- 
perature, and  not  liable  to  sudden  transi- 
tions from  one  extreme  to  the  other. 

BAROMETRIC   FORMULAS. 

Even  if  the  observations  have  been 
made  under  the  most  favorable  condi- 
tions of  atmosphere,  elevation  and  loca- 


134 

tion,  and  are  perfect  as  far  as  human  in- 
telligence can  make  them  so,  that  is,  free 
from  all  personal  and  instrumental  er- 
rors, there  yet  remains  a  consideration 
which  may  materially  affect  the  com- 
pleted altitude.  The  same  observations, 
reduced  by  different  formulas,  will  give 
results  in  some  cases  widely  different, 
the  discrepancy  between  the  returns  of 
two  well-authorized  methods  of  compu- 
tation frequently  amounting  to  the  sum 
of  the  real  errors  of  both;  this  is  ex- 
emplified in  the  following  determination 
of  the  height  of  Corcovado,  in  which  one 
system  of  reduction  gives  an  altitude 
above  the  true  one,  and  the  other  places 
it  too  low. 

The  barometric  formula  is  composed 
of  several  terms,  each  of  which  is  a  com- 
bination of  some  physical  constants,  such 
as  the  relative  weight  of  air  and  mercury, 
or  the  variation  of  gravity  with  latitude, 
and  some  of  the  barometrical  data,  as 
the  temperature  or  moisture  of  the  at- 
mosphere. Of  these  formulas,  there  are 
two  general  classes,  based  upon  the  equa- 


135 

tions  of  Laplace  and  Bessel.  Not  only 
do  they  differ  in  those  constant  quanti- 
ties upon  which  all  barometrical  determ- 
inations must  depend,  but  also  in  the 
presence  or  absence  of  an  entire  term,  as 
the  formula  of  Bessel  has  a  separate  fac- 
tor as  a  correction  for  the  humidity  of 
,the  air,  while  Laplace  includes  the  in- 
fluence of  the  aqueous  vapor  with  that 
of  temperature. 

Thus  it  will  be  seen  that  the  formula 
of  Laplace  is  more  convenient,  while  that 
of  Bessel  is  more  complete.  The  scien- 
tific world  has  found  it  difficult  to  choose 
between  them,  and  while  Delcros,  Guyot> 
and  others  have  accepted  the  formula  of 
Laplace,  that  of  Bessel  has  been  adopted 
by  Plantamour,  Williamson,  and  others. 
But  it  is  admitted,  even  by  those  who 
are  in  favor  of  the  former  method,  that 
the  constants  in  use  in  Bessel's  formula, 
as  modified  by  the  more  recent  arrange- 
ment of  Plantamour,  are  later  and  more 
reliable  than  those  accepted  by  Laplace, 
and  there  is  also  a  prevalent  opinion 
among  scientists  that  some  accuracy  has 


136 

been  sacrificed  to  convenience  in  La- 
place's method,  a  concession  which  it  may 
sometimes  be  justifiable  to  make  in  the 
application  of  a  formula,  but  never  in 
its  construction. 

The  advocates  of  each  system  have 
published  examples  showing  the  close 
accordance  of  their  results  with  altitudes 
determined  trigonometrically  or  by  spirit- 
level.  But  as  the  number  of  these  re- 
markable coincidences  is  about  equal  on 
each  side,  and  as  in  each  instance  the 
observations  would  have  given  results 
considerably  wrong  by  the  application  of 
the  other  formula,  they  prove  simply  two 
things;  first,  that  they  are  coincidences, 
and  that  to  certain  cases  the  method  of  La- 
place is  more  applicable,  while  to  others 
that  of  Plantamour  will  yield  better  re- 
turns; and  second3  that  it  is  quite  impos- 
sible to  devise  any  formula  that  will 
yield  an  accurate  solution  of  all  problems 
in  the  barometrical  measurement  of 
heights. 

Since  there  seems  to  be  a  preponder- 
ance of  evidence  and  a  growing  disposi- 


137 

tion  in  favor  of  Plantamour's  formula,  it 
has  already  been  adopted  by  the  Geo- 
logical Commission  as  a  basis  for  its 
barometrical  work,  and  its  several  terms 
have  been  developed  into  tables  for  the 
convenient  computation  of  altitudes. 
After  the  preparation  of  those  tables  and 
as  a  test  example  with  which  to  prove 
their  efficacy,  the  height  of  Corcovado 
Peak  was  determined  barometrically 
with  the  following  results: 

Metres. 

Altitude  of  Corcovado,  by  tables  of  the 
commission,  based  upon  Planta- 
mour's formula 705 .84 

By  Laplace's  formula 702.15 

Determined  by  triangulation 704.74 

Metres. 

Error  by  Plantamour's  formula +1.10 

"       Laplace's  "        —2.59 

Discrepancy  between  the  two 3.69 

The  foregoing  is  a  very  creditable  and 
satisfactory  barometrical  result,  and  is 
one  more  argument  in  favor  of  the  use 
of  Plantamour's  complete  formula. 

ALTITUDES    BY    VERTICAL    ANGLES. 

As  a   supplement   to   the   barometric 


138 

hypsometry,  every  theodolite,  whether 
for  meanders  or  triangulation,  is  fitted 
with  a  vertical  circle,  from  which  to  read 
the  angles  of  elevation  and  depression  of 
those  points  which  are  located  by  inter- 
sections, in  order  to  compute  the  heights 
of  the  same.  From  this  angle  and  the 
horizontal  distance  between  any  two 
peaks,  their  apparent  difference  of  alti- 
tude is  obtained  by  a  trigonometrical 
calculation,  and  then  a  correction  is  ap- 
plied for  earth's  curvature  and  refrac- 
tion. In  the  field  these  angles  are 
recorded  as  plus  or  minus,  according  as 
the  objective  point  is  above  or  below  the 
observer's  station,  whose  altitude  is  in- 
variably determined  by  barometric  read- 
ings. 

In  this  manner  the  heights  of  hund- 
reds of  points  throughout  the  field  of 
survey  are  found  with  an  accuracy 
nearly  equal  to  that  of  the  peak  from 
which  the  angle  is  taken.  Indeed,  a 
mean  altitude  derived  from  the  three 
angles  of  elevation,  read  from  three 
different  triangulation  stations,  will  give 


139 

the  altitude  of  the  point  of  intersection 
with  less  probable  error  than  that  of 
either  of  the  mountains  from  which  it 
was  derived. 

METEOROLOGY     IN    THE    SOUTHERN    HEMI- 
SPHERE. 

Brazil  stands  almost  alone  as  a  great 
civilized  country  lying  in  the  Southern 
hemisphere.  It  is  comprehensive  in  its 
latitude,  reaching  from  north  of  the 
equator  far  into  the  south  temperate 
zone.  From  this  unique  and  favorable 
position  upon  the  earth's  surface,  as  well 
as  from  the  liberal  patronage  bestowed 
by  its  government  upon  the  de- 
velopment of  science,  it  needs  no 
prophetic  eye  to  see  that  this  em- 
pire is  destined  to  become  one  of  the 
busiest  and  most  fruitful  fields  of  scien- 
tific research.  Especially  is  this  the  case 
in  the  investigation  of  those  great  ques- 
tions concerning  the  terrestial  shape  and 
dimensions,  and  those  others,  still  more 
numerous,  which  from  the  form  of  the 
earth,  or  from  other  and  unknown 


140 

causes,  vary  with  geographical  position. 
Important  among  the  latter  is  the  science 
of  meteorology,  whose  general  laws  are 
not  the  same  all  the  world  over,  but 
which  are  largely  influenced  by  latitude 
and  by  proximity  to  either  pole. 

The  following  extract  from  Colonel 
Williamson's  valuable  treatise  on  the 
barometer  and  its  uses,  will  illustrate 
the  absence  and  the  need  of  meteorologi- 
cal observations  south  of  the  equator: 

"  It  has  been  determined  by  actual  ob- 
servations, and  confirmed  by  theory,  that 
the  sea-level  pressure  varies  in  different 
latitudes  by  a  definite  law,  modified  in 
practice  by  local  peculiarities  of  climate. 
It  has  been  found  that  the  mean  baro- 
metric pressure  is  less  in  the  immediate 
vicinity  of  the  equator,  and  it  increases 
towards  the  north  to  -between  latitude 
30°  and  35°  where  it  is  greatest.  It  then 
gradually  decreases  to  about  latitude  60 °, 
and  from  there  towards  the  north  pole 
there  is  a  slight  increase.  In  the  south- 
ern hemisphere,  where  the  observations 
have  been  less  numerous,  the  mean 


141 

pressure  seems  to  increase  to  between 
20°  and  30°  of  south  latitude,  when  it 
gradually  decreases  to  about  42°,  and 
then  commences  a  remarkable  fall,  so 
that  towards  the  south  pole,  the  mean 
pressure  is  said  to  be  less  than  29 
inches."* 

In  the  table  of  mean  heights  of  the 
barometer  at  the  sea-level,  given  in 
various  works  on  meteorology,  there  are 
but  two  stations  south  of  the  equator; 
these  are  Rio  de  Janeiro  and  the  Cape  of 
Good  Hope.  In  north  latitude,  however, 
the  list  comprises  more  than  thirty 
places  at  which  this  determination  has 
been  satisfactorily  accomplished,  by 
years  of  observations,  and  these  are 
favorably  situated  at  intervals  between 
the  equator  and  the  pole. 

Again,  while  the  horary  oscillation  in 
the  atmospheric  pressure  is  greatest 
near  the  equator,  and  diminishes  thence 
each  way  to  the  poles,  the  abnormal 
oscillation  is  least  in  regions  of  small 

*  T36.6  millimetres. 


142 

latitude,  and  increases  with  the  distance 
from  the  equator.  As  the  latter  is 
the  more  incomprehensible  and  less 
regular  of  the  two,  and  consequently  the 
greater  source  of  error,  it  would  appear 
that,  in  general,  barometrical  work  would 
be  most  reliable  in  tropical  regions,  and 
hence  this  system  of  hypsometry  would 
be  especially  applicable  to  Brazil.  And, 
in  addition  to  their  immediate  and  prac- 
tical use  in  the  construction  of  maps,  the 
meteorological  results  of  a  survey  of  the 
proposed  nature,  taken  at  low  and  high 
altitudes,  at  the  sea-coast  and  in  the 
remote  inland,  with  permanent  stations 
at  intervals  where  long  series  of  obser- 
vations would  be  accumulated,  would 
form  a  basis  upon  which  to  establish  the 
general  laws  of  barometric  fluctuation 
throughout  this  vast  portion  of  the 
Southern  hemisphere. 

CONTINGENCIES    IN   THE    SURVEY. 

The  foregoing  are  the  general  divi- 
sions and  some  of  the  novel  features  of 
the  geographer's  work  in  the  field. 


143 

While  these  are  sufficient  to  carry  the 
survey  across  any  ordinary  country,  cer- 
tain districts  may  be  encountered  in 
which  these  methods  may  not  be  easily 
applicable.  It  is  impossible,  in  a  paper 
of  this  nature  and  length,  to  foresee  and 
provide  for  all  of  the  emergencies  that 
may  arise;  it  is  necessary  for  the  geog- 
rapher to  first  see  his  territory,  and  then, 
if  he  is  a  true  engineer,  he  will  be  able 
to  devise  some  means  of  survey  which 
will  be  competent  to  meet  the  difficulties, 
however  great  they  may  be. 

For  instance,  it  may  be  asked  how  a 
survey  based  upon  triangulation  can  be 
carried  across  the  smooth  and  unbroken 
table-lands  of  a  country.  The  answer 
will  be  that  the  plains  are  not  usually  so 
broad  that  they  cannot  be  spanned  by 
the  length  of  a  triangle-side  ;  and, 
furthermore,  if  there  are  no  eminences 
that  can  be  used  for  triangulation  points, 
so  much  less  is  there  need  for  this  system 
of  survey.  Over  the  smooth  plain  it  is 
possible  to  travel  in  straight  lines,  such 
being  the  usual  character  of  roads  in  a 


144 

level  country,  and  since  a  meander  by 
direct  routes  is  reliable,  the  survey  can 
proceed  from  one  known  point  to  the 
next  with  comparative  accuracy,  tracing 
in  the  rivers,  lakes,  and.  other  geographi- 
cal features  as  it  goes.  As  a  rough, 
mountainous  country  is*its  own  remedy, 
furnishing  a  great  number  of  advantage- 
ous stations  for  the  survey,  so,  with  the 
absence  of  these  mountains,  vanishes  in 
great  part  the  labors  and  difficulties  of 
this  work. 

THE    STADIA,    OK  TELEMETER. 

Although  the  stadia,  or  telemeter  pro- 
cess, is  too  slow  for  the  general  prosecu- 
tion of  a  geographical  survey,  there  may 
be  occasional  areas  in  which  the  previous 
methods  will  fail,  and  this  will  suffice. 
The  direct  linear  survey  of  a  river,  by 
this  means,  has  already  been  mentioned. 
As  another  illustration,  take  the  case  of 
a  valley — as,  for  instance,  the  valley  of 
the  Amazon — which  is  so  broken  with 
lakes,  swamps,  and  the  many  channels 
and  arms  of  the  river,  that  its  islands 


145 

and  shores  cannot  be  reached  and  located 
by  any  means  of  direct  measurement; 
and  where,  farther,  the  vegetation  is  so 
abundant  and  dense,  that  ordinarily  no 
three  fixed  points  are  visible  from  the 
water's  edge.  Here  the  telemeter  may 
be  the  only  instrument  by  which  the  re- 
quired distances  may  be  obtained.  The 
observer,  establishing  his  instrument  in 
open  ground,  from  which  triangulation 
stations  can  be  seen,  sends  his  assistant, 
in  a  boat  or  otherwise,  to  such  points 
along  the  water  as  may  be  in  sight. 
These  he  locates  by  single  observations, 
reading  the  distances  from  the  rod  held 
by  the  assistant.  Thus  the  telemeter 
station  is  referred  to  the  observer's  posi- 
tion, which,  in  its  turn,  can  be  fixed  by 
means  of  three- point  observations  upon 
the  triangulation  stations  of  the  border- 
ing cliffs. 

In  this  simple  and  ingenious  way  of 
determining  distances  by  single  observa- 
tions, it  is  necessary  that  the  diaphragm 
of  the  telescope  of  the  observer's  instru- 
ment should  be  fitted  with  two  horizon- 


146 

tal  cross-wires,  and  that  his  assistant 
should  be  furnished  with  a  graduated 
rod,  or  telemeter.  Then  looking  through 
the  telescope,  the  projection  of  the  cross- 
wires  upon  the  rod  includes  a  certain 
amount  of  the  graduation.  This  is  a 
chord  subtending  a  certain  constant 
angle  in  the  line  of  collimation,  and,  by 
a  principle  in  geometry,  this  chord  in- 
creases directly  with  its  distance  from 
the  angle  which  it  subtends. 

THE    PLANE   TABLE. 

With  the  use  of  the  plane  table,  there 
comes  so  great  a  temptation  to  go  into 
the  details  of  the  work,  to  linger  over  a 
small  area,  and  to  finish  the  sheets  with 
a  topographical  completeness,  that  its  too 
general  adoption  will  be  found  to  retard 
the  progress  of  a  geographical  survey. 
In  addition,  it  is  cumbersome  in  its 
shape,  offering  a  broad  surface  of  ex- 
posure, and  for  that  reason  is  not  well 
fitted  for  service  upon  high  mountain 
stations,  where  the  wind  is  strong  and 
storms  are  frequent.  In  its  favor,  how- 


147 

ever,  it  must  be  said  that  this  instru- 
ment has  been  successfully  employed 
upon  the  extensive  geological  and  geo- 
graphical surveys  under  Major  J.  W. 
Powell,  of  the  United  States,  and  that 
very  favorable  reports  have  been  made 
concerning  its  usefulness.  The  incon- 
venience of  its  shape  has  been  modified 
in  this  service,  the  table  being  composed 
of  slats  hinged  together,  so  that  it  may 
be  folded  into  a  small  compass  for  the 
purpose  of  transportation. 

When,  in  the  course  of  a  work  of  this 
nature,  there  is  encountered  a  district 
where  the  importance  of  the  field  will 
justify  a  minute  and  laborious  survey, 
the  plane-table  will  serve  an  excellent 
purpose  there.  It  is  very  useful  in  the 
mapping  of  a  populous  district,  the 
suburbs  of  a  city,  a  mining  region,  or  in 
the  representation  on  large  scale  of  a 
piece  of  topography  which  is  interesting 
as  a  type  of  geological  structure.  It  is 
always  an  easy  matter  for  the  geogra- 
pher to  accommodate  himself  and  his 
methods  to  detailed  surveys  like  the 


148 

above,  and  it  is  a  mistaken  idea  to  sup- 
pose that  the  exploration  of  a  province, 
unfits  an  engineer  for  the  topographical 
delineation  of  a  parish.  In  all  work  of 
engineering  there  is  a  constant  tendency 
towards  greater  accuracy,  refinement, 
and  detail,  and  it  is  not  freedom  which 
the  geographer  enjoys,  in  neglecting  the 
minor  features  of  the  earth's  surface, 
but  rather  a  necessary  restraint  that  is 
imposed  upon  him,  to  keep  him  from 
sacrificing  the  important  to  the  unim. 
portant. 

THE    OFFICE   WORK. 

As  for  the  computations  and  other 
reductions  of  notes  which  follow  a  field 
season  of  the  survey,  there  is  not  space 
to  discuss  them  here,  nor  is  there  any 
special  need  of  such  a  discussion,  as  they 
do  not  differ  materially  from  those 
which  apply  to  geodetic  work  in  general. 
Nor  are  the  duties  of  the  draughting- 
room  greatly  distinguished  above  the 
customary  routine  of  such  office  work. 
This  thing  only,  may  be  noticed,  that 


149 

the  hand-to-hand  struggle  which  the 
field  engineer  constantly  sustains  with 
the  forces  and  obstacles  of  nature  blunts 
the  delicacy  of  his  touch,  and  makes  his 
hand  too  heavy  for  the  fine  drawing 
necessary  in  a  map  finished  for  publica- 
tion, and  there  should  be  in  every  office 
a  superior  draughtsman  who  is  accus- 
tomed to  the  use  of  no  heavier  imple- 
ment than  the  artist's  pen. 

This  artistic  finish  is  bought  by  some 
sacrifice  of  accuracy,  however,  and  be- 
tween the  field  engineer  and  the  final 
draughtsman  there  should  be  few,  if  any, 
middlemen  to  compile  and  replot  the 
work,  because  only  the  man  who  has 
seen  the  country  can  reproduce  its  physi- 
cal characteristics  with  truthfulness. 
In  every  copy  that  is  subsequently  made 
the  face  of  the  land  grows  more  artifi- 
cial and  ideal;  each  mountain  loses  its 
individuality  of  shape,  and  assumes  a 
symmetrical  regularity  which  it  does 
not  possess  in  nature;  some  of  the  nice- 
ties of  truthful  representation  are  mag- 
nified into  exaggeration,  and  others  are 


150 

overlooked  and  obliterated;  the  bed  of 
every  canon  grows  broader  in  each  suc- 
cessive transcript;  and  the  large  hills 
grow  larger  as  the  smaller  ones  dwindle 
away.  As  in  a  popular  parlor  game,  a 
whispered  story,  passing  current  from 
mouth  to  mouth  throughout  the  round 
of  a  circle,  grows  strange  and  distorted 
beyond  recognition,  so  in  the  successive 
reproductions  of  a  map  by  strange 
hands,  it  loses  its  photographic  truth  of 
execution  as  the  idiosyncracies  of  the 
various  draughtsmen  are  wrought  into 
the  plan.  Finally  it  comes  to  represent 
a  country  that  is  unnatural  in  its  regu- 
larity, made  not  so  much  by  the  acci- 
dents of  nature  as  by  the  design  of 
man,  and  moulded  by  the  rules  of  a  uni- 
form and  rigid  geometry. 

PLOTTING  THE  NOTES. 

It  is  necessary  that  each  engineer 
shall  plot  his  own  notes,  as  he  alone  is 
familiar  with  their  arrangement  through- 
out his  books,  and  only  he  is  able  to  de- 
rive the  full  benefit  from  them.  There- 


151 

fore  during  the  office  season  he  will  be 
engaged  upon  a  contour  plot  of  the  area 
which  he  has  surveyed  during  the  pre- 
ceding half  of  the  year.  Here  he  will 
collect  and  compile  in  graphic  shape  all 
of x  the  information  which  lies  scattered 
throughout  the  dozen  note  and  sketch- 
books which  represent  his  labors  in  the 
field.  Upon  this  map  fine  drawing  will 
not  be  so  essential  as  truthful  representa- 
tion and  the  utmost  accuracy  of  position 
that  can  be  attained  from  the  material 
at  hand;  an  inaccuracy  that  is  barely 
apparent  upon  the  paper  will  correspond 
to  a  very  large  error  in  the  field,  and  so 
a  moment's  oversight  in  the  office  may 
invalidate  the  scrupulous  care  of  a  day's 
or  week's  work  upon  the  survey. 

These  sheets  will  be  the  basis  of  all 
the  maps  of  the  survey,  no  matter  in 
what  shape  they  may  be  published,  and 
hence  the  urgency  of  having  them  correct 
in  all  of  their  positions,  statements  and 
figures,  and  so  complete  as  to  include 
every  detail  upon  the  pages  of  the 
sketch-books,  down  to  the  shape  of  a 


152 

mountain-spur  or  village,  or  the  presence 
of  a  spring  of  water  or  dwelling  place. 
As  the  expense  of  sustaining  an  engineer 
in  the  field  is  at  least  double  the  cost  of 
his  office-work,  he  should  confine  himself 
to  what  is  absolutely  necessary  in  the 
collection  of  his  notes,  and  then  utilize 
even  the  least  of  these  in  his  subsequent 
plotting  and  development  of  them. 

CONTOUR  PLOTS. 

The  plots  will  be  constructed  in  con- 
tour lines,  as  that  is  the  only  method  in 
which  the  engineer  can  give  precise  ex- 
pression to  his  information  and  impress- 
ions concerning  the  heights,  slopes,  and 
forms  of  the  country  that  he  has  sur- 
veyed. While  a  map  executed  in 
hachures  would  be  more  artistic  and 
more  pleasing  to  the  eye,  it  cannot  be 
made  so  mathematically  invariable  in  its 
conveyance  of  ideas,  that  is,  it  cannot  be 
made  to  convey  the  same  ideas  to  all 
persons;  the  bluff  that  would  seem  high 
to  one  observer  would  seem  low  to 
another,  and  the  depth  of  shade  that 


153 

would  represent  a  steep  gradient  to  one 
draughtsman  would  stand  for  a  moderate 
declivity  to  another,  according  to  their 
peculiarities  of  judgment,  or  to  the 
different  schools  of  drawing  in  which 
they  had  been  educated.  The  most 
skilled  cartographer,  with  one  of  the 
best  of  hachure  maps  before  him,  would 
find  it  difficult  to  estimate  the  angle  of 
any  mountain  slope,  or  to  tell  which  of 
two  neighboring  peaks  was  the  highest, 
unless  their  heights  were  given  in  figures. 
In  a  glance  at  a  contour  plot,  however, 
he  could  count  the  excess  of  lines  in  one 
of  these  mountains,  and  so  compute  its 
superior  altitude;  or  note  the  number  of 
lines  in  a  centimeter  of  space,  and  so 
determine  the  gradient  of  the  earth's 
surface  there.  For  this  reason  the  con- 
tour plot  is  the  only  true  basis  from 
which  subsequent  maps  can  be  made; 
then,  no  matter  how  many  field  engi- 
neers may  contribute  to  this  work,  their 
reports  will  all  come  to  the  compiler  and 
final  draughtsman,  written  in  the  uniform 
language  of  lines  at  regular  vertical  in- 


154 

tervals.  Otherwise,  if  the  plots  were  in 
hachures,  this  draughtsman  would  find 
it  well-nigh  impossible  to  so  assimilate 
them  that  his  finished  map  would  not 
reveal  traces  of  the  many  different  hands 
from  which  it  originated. 

FINAL  MAPS. 

Unless  the  contour  lines  are  so  numer- 
ous and  close  together  as  to  produce 
striking  contrasts  of  light  and  shade  as 
the  slope  varies,  this  map  has  no  mean- 
ing to  the  popular  eye.  The  ordinary 
observer  sees  in  it  only  a  maze  and  con- 
•f  vision  of  lines,  of  whose  design  and 
importance  he  is  ignorant,  and  so  it  is  of 
no  assistance  to  him.  Therefore,  since 
maps  are  usually  published  for  the  in- 
formation and  guidance  of  the  people  at 
large,  it  is  wise  that  they  should  be 
drawn  with  hachure  shading,  which 
gives  a  more  intelligible  but  less  precise 
picture  of  the  country.  In  the  construc- 
tion of  this,  the  contours  of  the  engineer's 
plot  are  so  many  guide-lines  to  the 
draughtsman,  who  graduates  the  light 


155 

and  darkness  of  the  shade  to  accord  with 
the  divergence  or  approach  of  these 
wavering  lines. 

In  addition  to  these  a  map  in  contours 
may  also  be  issued  for  the  use  of  engi- 
neers, the  projectors  of  railways,  and, 
more  especially,  as  a  basis  of  the  geo- 
logical and  resource  charts,  to  which 
this  system  is  peculiarly  adapted,  as  its 
lines  of  equal  level  are  of  great  assist- 
ance in  determining  the  extent  of  the 
various  formations,  and  for  depicting 
those  areas  of  vegetable  growth  which 
are  bounded  by  fixed  limits  of  altitude. 
The  dip  and  strike  of  a  bed  of  uniform 
slope  being  given  at  any  one  point  of  its 
outcrop,  it  is  an  easy  matter  to  trace 
upon  this  map  its  line  of  reappearance 
upon  the  farther  side  of  a  mountain- 
range,  or  at  any  other  point  at  which  it 
may  be  exposed  again.  Or,  by  counting 
the  lines  of  vertical  equi-distance,  the 
geologist  learns  the  thickness  of  the  vari- 
ous strata,  the  extent  of  a  fault,  or  any 
other  fact  in  geological  dimensions. 


156 

REVIEW    OF   THIS   METHOD    OF    SURVEY. 

In  this  paper  the  writer  is  at  a  disad- 
vantage in  appearing  to  advocate  inac- 
curate methods,  and  perhaps,  at  times, 
actuated  by  a  desire  to  give  a  perfectly 
frank  and  honest  expose  of  the  subject 
under  discussion,  he  has  magnified  the 
amount  of  inaccuracy  to  which  the 
operations  described  in  these  pages 
would  be  liable;  at  all  events  he  has 
been  very  liberal  in  his  allowance  for 
probable  error.  Indeed,  to  those  who 
have  been  in  the  habit  of  reading,  and 
believing,  barometrical  altitudes  that  are 
given  down  to  the  tenth  of  a  foot,  or 
sextant  determinations  to  the  hundredth 
of  a  second,  it  may  appear  unpardomibly 
liberal  to  allow  for  an  error  of  meters  or 
seconds  in  these  classes  of  work,  and 
perhaps  to  some  it  may  seem  indicative 
of  professional  unfitness  in  the  engineer 
who  would  acknowledge  the  liability  of 
such.  But  while  results  like  the  above 
are  frequently  published,  their  authors 
would  be  either  sciolists  or  charlatans  if 
they  were  to  claim  that  they  were  abso- 


157 

lately  reliable  down  to  those  small 
fractions;  it  is  often  the  custom  among 
the  most  conscientious  and  intelligent 
engineers  to  make  their  reports  in  that 
elaborated  form,  since  those  are  the 
figures  at  which  their  computations 
finally  arrived,  and  hence  there  are  cer- 
tain weights  of  probability  in  their 
favor. 

In  like  manner,  in  the  computations  of 
a  survey  of  the  proposed  nature,  it  would 
never  be  allowable  to  neglect  or  throw 
away  any  odd  figure  or  fraction,  on  the 
plea  that  it  was  probably  exceeded  by 
the  error  of  the  whole.  By  following 
this  system,  not  only  are  habits  of  accu- 
racy inculcated  and  sustained  among  the 
assistants  of  a  survey,  but  the  closest 
possible  approximation  to  the  truth  is  at- 
tained. 

In  the  ordinary  branches  of  his  profes- 
sion, habits  of  rigid  precision,  at  what- 
ever cost  of  time  and  money,  are  the 
best  recommendations  for  an  engineer. 
In  a  geographical  survey,  however,  to 
enforce  this  rule  beyond  .the  triangula- 


158 

tion,  upon  which  the  integrity  of  the 
whole  depends,  and  to  continue  it  in  full 
force  throughout  all  of  the  subordinate 
branches  of  the  work,  would  be  to  make 
such  a  survey  impossible  in  Brazil,  owing 
to  the  enormous  expense  that  would  at- 
tend it.  Viewed  theoretically,  the  best 
of  maps,  even  those  produced  by  the 
tedious  processes  of  the  European  topo- 
graphical surveys,  are  but  approxima- 
tions to  the  truth;  the  question  now 
arises  as  to  how  close  it  is  profitable  to 
bring  this  approximation.  Viewed  prac- 
tically, the  maps  that  would  result  from 
the  proposed  system  of  survey  would  be 
seldom,  if  ever,  in  error  to  a  perceptible 
degree,  and  it  would  seem  that  this  is 
the  limit  of  accuracy  bayond  which  this 
country  cannot  well  afford  to  go. 

To  condemn  a  method  of  surveying 
because  it  is  not  absolutely  accurate 
would  be  to  condemn  all  of  the  survey 
of  the  world,  and  especially  all  of  the 
systems  of  ordinary  land  surveying, 
which  are  so  faulty  that  it  is  very  sel- 
dom that  a  purchaser  of  land  does  not 


159 

get  either  considerably  more  or  less  than 
he  pays  for.  Still,  that  has  not  been 
deemed  sufficient  reason  why  all  buying 
and  selling  of  real  estate  should  cease 
until  its  boundaries  could  be  determined 
by  the  instrumentality  of  such  rods,  com- 
pensated for  temperature  or  packed  in 
ice,  as  are  used  in  the  measurement  of 
geodetic  base-lines.  In  one  respect  the 
proposed  system  is  far  superior  to  the 
land  survey,  as  it  is  founded  upon  the 
principle  of  triangulation,  which,  secur- 
ing it  in  its  true  proportions,  prevents 
any  great  accumulation  of  error.  In  the 
United  States  of  North  America,  where 
surveys  of  this  nature  are  in  active  and 
successful  operation,  it  has  been  earnestly 
advocated  that  the  triangulation  of  the 
geographical  survey  should  be  made  the 
basis  of  the  land  survey,  the  different 
triangulation  stations  serving  as  initial 
points  from  which  to  run  the  land  bound- 
aries, and  it  is  very  probable  that,  with- 
in a  year  or  two,  this  plan  will  be 
adopted  there. 
There  are  different  degrees  of  accu- 


160 

racy,  each  adapted  to  the  end  which  it  is 
intended  to  serve;  this  degree,  explained 
here,  is  sufficient  for  the  rapid  prepara- 
tion of  a  very  useful  and  complete 
geographical  map.  It  would  not  suffice 
for  the  measurement  of  an  arc  of  the 
meridianr  such  as  has  been  proposed  for 
this  empire.  That  is  a  work  in  which 
no  error,  however  small,  that  is  not  be- 
yond the  cognizance  of  the  human 
senses  and  judgment,  can  be  excused  or 
overlooked.  To  publish  a  wrong  result 
here  would  be  not  only  a  national  dis- 
grace, but  a  misfortune  to  the  whole 
world,  as  it  is  upon  the  shape  and  dimen- 
sions of  the  earth  that  many  of  our 
geodetic  and  other  scientific  formulas 
rest,  while  it  is  from  the  same  source 
that  the  world  derives  its  standard  unit 
of  length,  by  which  the  interests  of  all 
civilized  people  are  affected.  Or,  if 
Brazil  were  prepared  to  enter  into  that 
honorable  rivalry  in  geodetic  work,  in 
which  some  of  the  older  nations  are  en- 
gaged, each  seeking  to  produce  instru- 
ments, methods,  results,  discoveries,  and 


161 

developments  that  may  be  in  advance  of 
everything  hitherto  achieved,  this  sys- 
tem of  survey  would  not  be  recom- 
mended. It  is  not  impossible,  however, 
that,  from  this  as  a  beginning,  there 
might  grow,  keeping  pace  with  the  gen- 
eral progress  of  the  country,  a  geodetic 
institution  that  would  be  equal  to  the 
best. 

ORIGIN    OF   THIS    SYSTEM. 

The  writer  by  no  means  pretends  to  be 
the  inventor  of  the  combination  of 
methods  described  in  these  pages,  al- 
though hitherto  there  has  been  but  little 
description  of  them  in  print.  An  effi- 
cient system  of  survey  cannot  be  the  in- 
vention of  any  one  man;  it  must  be  the 
outgrowth  of  years  of  practical  expe- 
rience, resulting  in  the  gradual  accumu- 
lation of  ideas  and  improvements  con- 
tributed by  those  who  have  been  en- 
gaged upon  it.  This  one  is  the  result  of 
a  growth  of  at  least  a  quarter  of  a  cen- 
tury, and  therefore  is  not  open  to  the 
serious  objection  of  being  new  and  un- 


162 

tried.  During  that  length  of  time,  the 
enterprise  of  geographical  surveying 
has  been  receiving  more  and  more  en- 
couragement from  the  government  of 
the  United  States,  which  has  wisely 
adopted  that  plan,  in  connection  with 
geological  and  other  scientific  research, 
as  a  means  of  opening  and  illustrating 
its  vast  public  territory. 

At  the  present  day  there  are  actively 
engaged  upon  this  duty  in  that  country 
three  important  commissions  of  survey. 
That  of  Dr.  F.  V.  Hayden,  geologist  in 
charge,  is  known  throughout  the  world 
by  its  extensive  and  important  work,  not 
only  in  geology  and  geography,  but  in 
all  their  kindred  sciences  as  well.  A 
second  is  under  Major  J.  W.  Powell,  the 
intelligent  geologist  and  intrepid  ex- 
plorer who  was  the  first  to  descend  the 
great  canon  of  the  Colorado  River.  An- 
other, more  strictly  geographical  in  its 
nature,  is  under  the  auspices  of  the  War 
Department,  and  is  conducted  by  Lieut. 
George  M.  Wheeler,  an  officer  of  envia- 
ble reputation  in  the  United  States  Corps 


163 

of  Engineers.  While  the  general  plan 
is  much  the  same  throughout  these 
three  commissions,  it  is  especially  to  his 
former  associates,  the  geographers  and 
officers  of  the  last-named  organization, 
that  the  writer  wishes  to  acknowledge 
his  indebtedness  for  whatsoever  of  value 
there  may  be  in  this  paper. 

BRAZIL    AND    THE    UNITED    STATES. 

Although,  as  has  been  stated  hereto- 
fore, it  is  not  wise  for  any  nation  to  copy, 
blindly,  and  without  adaptation  to  its 
own  peculiar  needs,  the  system  of  sur- 
vey employed  by  any  other  country,  yet 
it  would  seem  that  the  processes  that  are 
fitted  to  the  United  States  would  require 
but  little  modification  to  be  adapted  to 
use  in  Brazil,  so  analogous  are  the  two 
countries  in  many  respects.  They  have 
equal  amounts  of  territory  as  near  as 
may  be,  but,  peopling  this  territory, 
there  are  four  times  as  many  inhabitants 
in  the  United  States  as  there  are  in 
Brazil;  thus  it  would  seem  that  the  me- 
thods that  are  deemed  sufficient  for  the 


164 

former  would  certainly  suffice  for  the 
latter.  In  each  country  the  population 
diminishes  from  a  thickly-settled  sea- 
coast  back  into  an  uncivilized  and  almost 
unknown  interior.  In  each  of  these 
there  is  a  great  amount  of  wild  land 
which  the  government  is  anxious  to  open 
to  colonization  and  cultivation.  To  ex- 
pose and  popularize  the  natural  wealth 
of  this  public  domain,  the  U.  S.  Govern- 
ment resorted  to  the  plan  of  scientific 
surveys,  to  which  the  Geological  Com- 
mission of  Brazil  is  very  similar  in  all 
respects,  and  so  efficiently  have  they 
accomplished  their  purpose  that  it  has 
become  a  noticeable  fact  in  the  cartog- 
raphy of  the  United  States  that  its  maps 
of  some  of  the  remote  and  unsettled  dis- 
tricts of  the  Rocky  Mountains  are 
superior  to  those  of  its  oldest  and  richest 
States,  and,  therefore,  there  are  now 
plans  on  foot  looking  to  the  extension  of 
these  geographical  surveys  over  the  en- 
tire surface  of  the  country. 

As  the  American  manner  of  railway- 
building,  more  expeditious  and  involving 


165 

less  first  cost  than  the  European  methods, 
has  been  found  practicable  in  Brazil,  in 
some  instances,  in  which  all  other  plans 
would  fail,  so  with  this  question  of  geo- 
graphical surveys,  it  may  prove  to  be  the 
American  system  or  none. 

RESULTS  OF  THIS  SYSTEM. 

Considering  now  the  results  that  could 
be  expected  from  such  a  geographical 
survey  of  Brazil,  this  question  can  be 
best  answered  by  referring  to  areas  sur- 
veyed in  the  same  manner  in  the  United 
States.  From  Lieut.  Wheeler's  annual 
report,  which  the  writer  has  before  him, 
it  appears  that  in  six  years'  continuance 
of  his  commission  an  approximate  extent 
of  800,000  square  kilometres  has  been 
surveyed.  Allowing  an  average  of  five 
parties  in  the  field  during  that  time,  the 
season's  work  of  one  engineer  reduces 
itself  to  about  25,000  square  kilometres. 
Allowing  proportional  returns  from  the 
various  other  geographical  surveys  at 
present  in  commission,  or  that  have  been 
in  existence  during  the  last  ten  years  in 


166 

the  western  portion  of  the  United  States, 
it  appears  that  one-third  of  the  area  of 
that  great  country  has  been  thus  sur- 
veyed in  that  period. 

This  is  at  a  total  expenditure  which, 
while  including  the  cost  of  all  other 
concomitant  scientific  labors,  to  which 
the  geographical  work  has  been  in  large 
part  incidental  and  tributary,  has  never 
exceeded  four  hundred  contos  ($  200,000) 
per  year.  There  is  probably  no  other 
department  of  public  enterprise  which 
has  yielded  so  extensive  and  valuable  re- 
turns for  an  equal  amount  of  money. 

AN  ESTIMATE  FOR  ONE  SEASON. 

In  general,  an  area  of  from  10,000  to 
30,000  square  kilometres,  varying  ac- 
cording to  the  geographical  nature  of 
the  country,  is  assigned  to  each  party 
for  a  season  of  four,  five,  or  six  months, 
and  its  ability  to  satisfactorily  cover 
that  district  in  that  time  is  conceded. 
To  illustrate  the  possibility  of  such  rapid 
progress,  let  us  take  a  typical  area  of 
20,000  square  kilometres  and  see  what 


167 

can  be  done  with  it  by  one  party  and 
one  geographer  in  one  season's  work  of 
six  months  in  duration.  Of  this  time 
the  first  month  will  be  consumed  in  the 
measurement  and  development  of  the 
base,  and  in  other  preparation.  Of  the 
remaining  period  one  month  more  will 
perhaps  be  lost  in  unavoidable  delays 
resulting  from  storms  or  other  causes. 
There  will  then  remain  four  months, 
which,  at  twenty-five  available  days  in 
each,  will  afford  one  hundred  days  for 
active  service  in  the  field. 

Allow  one  half  of  these  days  for  the 
meander  survey,  and  the  other  half  for 
the  occupation  of  mountain  stations. 
Fifty  mountain  stations  will  thus  result, 
and,  in  addition  to  these,  there  will  be  a 
topographical  station  either  upon  or 
adjacent  to  each  day's  meander.  So 
there  are  one  hundred  triangulation  and 
topographical  stations  distributed  at 
judicious  intervals  over  this  territory. 
That  is,  there  is  one  for  every  two 
hundred  square  kilometres  of  ground,  or, 
typically,  they  are  but  about  fourteen 


168 

kilometres  apart,  and  the  piece  of  coun- 
try to  be  sketched  in  contours  need  not 
extend  more  than  seven  kilometres  in 
each  direction;  this  estimate  ignores  the 
meander  surveys,  to  which  fifty  days  of 
the  season  will  be  devoted,  and  by  which 
these  stations  will  be  separated  and  sur- 
rounded. 

At  twenty-five  kilometres  a  day,  a  very 
reasonable  allowance,  the  total  distance 
of  meander  route  will  be  1250  kilometres. 
This  distance  would  reach  across  our 
area  nine  times,  cutting  it  into  strips  of 
sixteen  kilometres  in  width.  Hence,  in 
order  to  include  the  entire  country  from 
this  survey,  the  typical  zone  of  each 
meander  would  not  reach  more  than 
eight  kilometres  on  either  side  of  its 
path;  but,  since  it  would  be  superfluous 
to  sketch  from  this  base  the  country  in 
the  immediate  vicinity  of  the  mountain 
stations,  these  plots  en  route  need  never 
extend  more  than  four  kilometres  from 
the  central  line.  Of  course,  in  practice, 
these  surveys  will  not  be  thus  distributed 
in  straight  lines  at  equal  distances  apart, 


169 

but  will  communicate,  intersect,  and 
duplicate  in  every  possible  way.  Still 
the  meander  will  serve  its  original  pur- 
pose of  penetrating  those  regions  and 
traversing  those  border-lands  that  are 
remote  from  the  mountain  stations,  and 
will  trace  out  the  roads,  trails,  and  im- 
portant streams,  whose  entire  length  in 
this  area  will  not  be  likely  to  exceed 
1250  kilometres. 

Returning  to  the  office  at  the  end  of  the 
season,  the  engineer  will  have  material 
enough  to  make  a  plot  of  the  country  on 
a  scale  of  one  centimetre  to  the  kilo- 
metre (100*000)?  or  one-half  a  centimetre 
to  the  kilometre  (^-oSror)'  Or,  to  put 
this  statement  with  more  precision,  he 
will  have  so  much  and  so  detailed  mate- 
terial,that  he  will  not  be  able  to  portray 
it  conveniently  and  intelligibly  on  a  scale 
of  less  than  3-^-^0  o-  But  when  the 
final  draughtsman  comes  to  copy  these 
plots,  he  may  condense  them,  if  it  be 
thought  expedient,  to  proportions  of 
TToVsr*  or  even  smaller.  On  the  other 
hand,  portions  of  this  area  may  be  plot- 


170 

ted  upon  a  much  larger  plan  than  any 
here  noticed,  should  such  be  found  nec- 
essary for  the  clear  and  complete  geo- 
graphical and  geological  representation 
of  the  same. 

EUROPEAN    SURVEYS. 

Now,  in  contradistinction  to  the  above 
showing,  let  us  take  up  the  reports  of 
some  European  surveys.  In  Prussia, 
12,000  square  kilometres,  a  little  more  or 
less,  are  surveyed  annually,  at  a  cost  of 
800,000  marks,  or,  as  near  as  may  be, 
four  hundred  contos  of  Brazilian  money,* 
exclusive  of  the  salaries  of  military  as- 
sistants; notice  that  in  the  United  States, 
with  a  total  annual  appropriation  not 
greater  than  this,  at  least  300,000  square 
kilometres  are  geographically  surveyed 
each  year,  this  territory  being  studied  at 
the  same  time  by  the  geologist,  the 
chemist  and  the  naturalist. 

Upon  the  Ordnance  Survey  of  Great 
Britain  there  were  over  1800  assistants 

*  A  conto  of  reis,  in  Brazil,  is  equal  to  about  five  hun- 
dred American  dollars,  or  a  hundred  pounds  sterling. 


171 

and  employes  engaged  during  the  year 
of  1874;  the  total  area  surveyed  by  them 
was  not  more  than  8,000  square  kilome- 
tres. With  the  methods  in  use  in  Austria 
an  experienced  topographer  can  survey 
in  one  field  season  of  six  months  five 
hundred  square  kilometres  at  the  farthest. 
In  Switzerland  the  topography  is  in  large 
part  done  by  contract,  and  it  alone,  ex- 
clusive of  triangulation  and  publication, 
costs  700  or  800  francs  per  square  stunde, 
or  about  twenty-two  mil  reis*  per  square 
kilometre.  So  with  the  surveys  of  Italy, 
Spain,  Sweden,  and  the  other  European 
countries  of  comparatively  small  extent; 
they  are  so  slow,  detailed,  and  withal  so 
expensive  as  to  be  inapplicable  to  the 
great  empire  of  Brazil. 

AX  ADVANTAGEOUS  DEVELOPMENT. 

So  vast  is  the  extent  of  this  empire 
that  the  idea  of  a  geographical  survey 
of  its  territory,  as  a  whole,  is  an  astound- 
ing one,  and  is  liable,  in  itself,  to  forbid 
all  further  consideration  of  the  subject. 

*  Eleven  American  dollars. 


172 

But  this  plan  does  not  necessarily  imply 
the  regular  extension  of  this  survey  over 
the  whole  country,  irrespective  of  popu- 
lation and  wealth.  On  the  contrary  it 
would  devote  itself  at  first  to  such  areas 
as,  from  geological  or  other  economical 
reasons,  might  most  urgently  require  it, 
and  a  region  of  especial  interest  to  the 
geologist  would  be  surveyed  first  and 
with  especial  care,  to  the  neglect  or  even 
exclusion  of  those  great  stretches  of 
country  whose  structure  is  unvaried  and 
monotonous.  In  a  few  conditions  of  its 
plan,  as,  for  instance,  in  the  system 
adopted  in  the  projection  of  its  maps,  it 
might  provide  for  any  possible  ultimate 
extension,  but  in  other  respects  it  could 
operate  with  equal  facility,  in  whatever 
districts  might  be  assigned  to  it. 

Nor  does  this  plan  imply  the  necessity 
of  any  great  outlay  at  the  beginning,  but 
would  ask  to  start  upon  a  small  scale  at 
first,  with  a  view  to  gradual  growth  as  it 
proved  itself  worthy  of  encouragement. 
As  the  aim  of  this  project  would  be  not 
only  the  production  of  much-needed 


173 

maps,  but  also  the  introduction  of  these 
methods  of  survey  from  abroad,  and  the 
training  of  Brazilian  engineers  in  the  use 
of  the  same,  any  very  extensive  initial 
basis  would  prove  not  only  embarrassing 
at  first  but  also  probably  disastrous  in 
the  end.  A  survey  inaugurated  upon  a 
grandiose  scale  is  too  liable  to  exhaust 
the  patience  and  liberality  of  its  official 
patrons  before  it  can  exhibit  results  ap- 
parently equivalent  to  the  expenditure 
that  it  has  caused,  and  the  frequent  fate 
of  such  enterprises  is  that  they  are  dis- 
continued at  about  the  time  when,  their 
organization  being  successfully  com- 
pleted, they  are  prepared  to  enter  upon 
an  area  of  efficient  and  fruitful  labor; 
hence,  all  of  the  expense  of  organization 
and  other  preliminaries  becomes  a  total 
loss  to  the  government. 

On  the  other  hand,  some  of  the  rm>st 
important  surveys  of  the  world  have 
arisen  from  humble  beginnings.  Such  an 
enterprise  educates  its  own  members,  the 
assistant  engineer  of  one  season  becom- 
ing the  engineer  of  the  next,  and  so  on. 


174 

It  develops  gradually  and  with  a  healthy 
growth,  perfecting  its  own  methods,  and 
always  experimenting  upon  a  small  scale, 
so  that  it  is  never  liable  to  serious  disas- 
ter. And,  above  all,  by  its  early  pro- 
duction and  exhibition  of  results  com- 
mensurate with  its  size,  and  with  its 
cost,  which  is  insignificant  at  first,  it 
buys  the  right  to  be  continued,  en- 
couraged and  increased  from  year  to 
year. 

A    GEOLOGICAL    AND    GEOGRAPHICAL   SUR- 
VEY. 

There  are  two  very  good  arguments 
for  such  a  geographical  survey  in  connec- 
tion with  the  Geological  Commission  of 
Brazil ;  first,  its  necessity  to  the  geologi- 
cal survey,  as  explained  in  the  early  part 
of  this  paper;  and  second,  because  in 
sudh  a  connection  it  can  work  most 
economically  and  profitably.  With  a 
combination  of  these  elements  comes 
much  valuable  co-operation  between  the 
representatives  of  the  various  branches 
of  science,  and  this  is  constantly  acting 


175 

to  lessen  the  expense  and  increase  the  re- 
turns of  such  a  survey.  For  instance,  as 
the  meteorologist  of  the  engineering 
corps,  an  assistant  with  some  acquaint- 
ance with  geology,  could  be  chosen.  As 
his  meteorological  duties  upon  the  march 
would  be  but  light,  he  could  devote 
much  of  his  time  to  a  geological  study 
of  the  road,  leaving  the  regular  geologist 
at  liberty  to  go  from  camp  to  camp  by 
any  other  route  that  he  might  select. 
Again,  the  meteorologist,  or  even  the  en- 
gineer himself,  may  make  strati  graphical 
sketches  upon  every  mountain,  and  bring 
specimens  of  rock  from  the  same,  while 
the  geologist  is  away  upon  some  detour 
to  regions  of  interest  in  another  direc- 
tion. 

Or,  reversing  this  illustration,  the 
geologist,  whose  profession  is  so  closely 
allied  to  that  of  the  geographer,  is  con- 
stantly making  notes  of  direction,  dis- 
tance, slope,  and  altitude,  which  are  of 
the  highest  importance  and  use  in  the 
construction  of  a  map.  These  are  lost 
to  the  world  if  there  is  not  an  accom- 


176 

panying  geographical  survey  into  whose 
plots  they  may  be  assimilated. 

In  witness  of  the  sympathy  with 
which  the  present  members  of  the  Geo- 
logical Commission  regard  geographical 
work,  and  of  their  skill  in  the  prosecu- 
tion of  the  same,  the  writer  would  men- 
tion their  intelligent  and  extensive  sur- 
veys of  the  valley  of  the  Amazon,  from 
Monte  Alegre  westwards,  and  of  its 
tributary,  the  Trombetas;  of  the  island 
of  Fernando  de  Noronha;  and  of  many 
localities  along  the  Atlantic  coast  and 
elsewhere  in  the  empire.  These  are  evi- 
dences of  a  willingness  and  an  ability  to 
collect  geographical  information,  which, 
in  themselves,  assure  the  success  of  a 
system  of  geographical  surveying  in 
connection  with  the  Geological  Commis- 
sion of  Brazil. 


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8vo,  cloth,  .  .  .  .  6  00 

6 


D.  VAN  NOSTRAND'S  PUBLICATIONS. 

WARD.  STEAM  FOR  THE  MILLION.  A  Popular 
Treatise  on  Steain  and  its  Application  to 
the  Useful  Arts,  especially  to  Navigation. 
By  J.  H.  Ward,  Commander  U.  8.  Navy. 
8vo,  cloth,  .  .  .  .  $1  00 

CLARK.  A  MANUAL  OF  RULES,  TABLES  AND 
DATA  FOR  MECHANICAL  ENGINEERS. 
Based  on  the  most  recent  investigations. 
By  Ban.  Kinnear  Clark.  Illustrated  with 
numerous  diagrams.  1012  pages.  8vo. 
Cloth,  $7  50;  half  morocco,  .  .  .  .1000 


JOYNSON.  THE  METALS  USED  IN  CONSTRUC- 
TION :  Iron,  Steel,  Bessemer  Metals,  etc, 
By  F.  H.  Joynson.  Illustrated.  12mo, 
cloth, 75 

DODD.  DICTIONARY  OF  MANUFACTURES,  MIN- 
ING, MACHINERY,  AND  THE  INDUSTRIAL 
ARTS.  By  George  Dodd.  12mo,  cloth,  1  50 

VON  COTTA.  TREATISE  ON  ORE  DEPOSITS.  By 
Bernhard  Von  Cotta,  Freiburg,  Saxony. 
Translated  from  the  second  German  ed., 
by  Frederick  Prime,  Jr.,  and  revised  by 
the  author.  With  numerous  illustrations. 
8vo,  cloth,  ....  ...  4  00 

PLATTNER.  MANUAL  OF  QUALITATIVE  AND 
QUANTITATIVE  ANALYSIS  WITH  THE  BLOW- 
PIPE. From  the  last  German  edition.  Re- 
vised and  enlarged.  By  Prof.  Th.  Richter, 
o  the  Royal  Saxon  Mining  Academy. 
Translated  by  Professor  H.  B.  Cornwall. 
With  eighty-seven  wood-cuts  and  lithogra- 
phic plate.  Third  edition,  revised.  668  pp. 
8vo,  cloth, 5  00 

PLYMPTON.  THE  BLOW-PIPE  :  A  Guide  to  its 
Use  in  the  Determination  of  Salts  and 
Minerals.  Compiled  from  various  sources, 
by  George  W.  Plympton,  C.  E.,  A.  M.,  Pro- 
fessor of  Physical  Science  in  the  Polytech- 
nic Institute,  Brooklyn,  N.  Y.  12mo,  cloth,  1  50 


D.  VAN  NOSTRAND'S  PUBLICATIONS. 

JANNETTAZ.  A  GUIDE  TO  THE  DETERMINATION 
OP  ROCKS  ;  being  an  Introduction  to  Lith- 
olqgy.  By  Edward  Jannettaz,  Doctenr  des 
Sciences.  Translated  from  the  French  by 
G.  W.  Plympton,  Professor  of  Physical 
Science  at  Brooklyn  Polytechnic  Institute. 
12mo,  cloth, $]  50 

MOTT.  A  PRACTICAL  TREATISE  ON  CHEMISTRY 
(Qualitative  and  Quantitative  Analysis), 
Stoichiometry,  Blowpipe  Analysis,  Min- 
eralogy, Assaying,  Pharmaceutical  Prepa- 
rations Human  Secretions,  Specific  Gravi- 
ties, Weights  and  Measures,  etc.,  etc.,  etc. 
By  Henry  A.  Mott,  Jr.,  E.  M.,  Ph.  D.  650  pp. 
HVO,  cloth, ,  .  6  00 

PYNCHON.  INTRODUCTION  TO  CHEMICAL  PHY- 
SICS ;  Designed  for  the  Use  of  Academies, 
Colleges,  and  High  Schools.  Illustrated 
with  numerous  engravings,  and  containing 
copious  experiments,  with  directions  for 
preparing  them.  By  Thomas  Ruggles  Pyn- 
chon,  D.  D.,  M.  A.,  President  of  Trinity  Col- 
lege, Hartford.  New  edition,  revised  and 
enlarged.  Crown  8vo,  cloth,  .  .  .  3  00 

PRESCOTT.  CHEMICAL  EXAMINATION  OF  ALCO- 
HOLIC J,IQUORS.  A  Manual  of  the  Constit- 
uents ott  he  Distilled  Spirits  and  Ferment- 
ed Liquors  of  Commerce,  and  their  Quali- 
tative and  Quantitative  Determinations. 
By  Alb.  B.  Prescott,  Prof,  of  Chemistry, 
University  of  Michigan.  12rno,  cloth,  .  1  50 

ELIOT  AND  STOKER,  A  COMPENDIOUS  MANUAL 
OF  QUALITATIVE  CHEMICAL  ANALYSIS.  By 
Charles  W.  Eliot  and  Frank  H.  Storer.  Re- 
vised, with  the  co-operation  of  the  Authors, 
by  William  Ripley  Nichols,  Professor  of 
Chemistry  in  the  Massachusetts  Institute 
of  Technology.  New  edition,  revised.  Il- 
lustrated. 12mo,  cloth 1  50 


D.  VAN  NOSTRAND'S  PUBLICATIONS. 

NAQUET.  LEGAL  CHEMISTRY.  A  Guide  to  the 
Detection  of  Poisons,  Falsification  of  Writ- 
ings, Adulteration  of  Alimentary  and  Phar- 
maceutical Substances ;  Analysis  of  Ashes, 
and  Examination  of  Hair,  Coins,  Fire-anna 
and  Stains,  as  Applied  to  Chemical  Juris- 
prudence. For  the  Use  of  Chemists,  Phy- 
sicians, Lawyers,  Pharmacists,  and  Ex- 
perts. Translated,  with  additions,  includ- 
ing a  List  of  Books  and  Memoirs  on  Toxi- 
cology, etc.,  from  the  French  of  A.  Naquet, 
by  J.  P.  Battershall,  Ph.  D. ;  with  a  Preface 
by  C.  F.  Chandler,  P^.  D.,  M.  D.,  LL.  D. 
Illustrated.  12mo,  cloth,  .  .  .  .  $2  00 

PRESCOTT.  OUTLINES  OP  PROXIMATE  ORGANIC 
ANALYSIS  for  the  Identification,  Separa- 
tion, and  Quantitative  Determination  of 
the  more  commonly  occurring  Organic 
Compounds.  By  Albert  B.  Prescott,  Pro- 
fessor of  Chemistry,  University  of  Michi- 
gan. 12mo,  cloth,  .  .  .  1  75 

DOUGLAS  AND  PRESCOTT.  QUALITATIVE  CHEM- 
ICAL ANALYSIS.  A  Guide  in  the  Practical 
Study  of  Chemistry,  and  in  the  work  of 
Analysis.  By  S.  H.  Douglas  and  A.  B. 
Prescott ;  Professors  in  the  University  of 
Michigan.  Second  edition,  revised.  8vo, 
cloth, 3  50 

RAMMELSBERG.  GUIDE  TO  A  COURSE  OF 
QUANTITATIVE  CHEMICAL  ANALYSIS,  ESPE- 
CIALLY OF  MINERALS  AND  FURNACE  PRO- 
DUCTS. Illustrated  by  Examples.  By  C. 
F.  Rammelsberg.  Translated  by  J.  Tow- 
ler,  M.  D.  8vo,  cloth, 2  25 

BEILSTEIN.  AN  INTRODUCTION  TO  QUALITATIVE 
CHEMICAL  ANALYSIS.  By  F.  Beilstein. 
Third  edition.  Translated  by  I.  J.  Osbun. 
I2mo.  cloth, 75 

POPE.  A  Hand-book  for  Electricians  and  Oper- 
ators. By  Frank  L.  Pope.  Ninth  edition. 
Revised  and  enlarged,  and  fully  illustrat- 
ed. 8vo,  cloth, 2  00 

9 


D.  VAN  NOSTRAND'S  PUBLICATIONS. 

SABINE.  HISTORY  AND  PROGRESS  OF  THE  ELEC- 
TRIC TELEGRAPH,  with  Descriptions  of 
some  of  the  Apparatus.  By  Robert  Sabine, 
C.  E.  Second  edition.  12mo,  cloth,  .  .  $1  25 

DAVIS  AND  RAE.  HAND  BOOK  OF  ELECTRICAL 
DIAGRAMS  AND  CONNECTIONS.  By  Charles 
H.  Davis  and  Frank  B.  Rae.  Illustrated 
with  32  full-page  illustrations.  Second  edi- 
tion. Oblong  8vo,  cloth  extra,  .  .  .  2  00 

HASKINS.  THE  GALVANOMETER,  AND  ITS  USES. 
A  Manual  for  Electricians  and  Students. 
By  C.  H.  Haskins.  Illustrated.  Pocket 
form,  morocco, „  .  150 

LARRABEE.  CIPHER  AND  SECRET  LETTER  AND 
TELEGRAPAIC  CODE,  with  Hogg's  Improve- 
ments. By  C.  S.  Larrabee.  18mo,  flexi- 
blecloth, 1  00 

GILLMORE  PRACTICAL  TREATISE  ON  LIMES, 
HYDRAULIC  CEMENT,  AND  MORTARS.  By 

§.  A.  Gillmore,  Lt.-Col.    U.  S.  Engineers, 
revet  Major-General  U.  S.  Army.    Fifth 
edition,  revised  and  enlarged.    8vo,  cloth,       4  00 
GILLMORE.  COIGNET  BETON  AND  OTHER  ARTIFI- 
CIAL STONE.    By  Q.  A.  Gillinore,  Lt.  Col. 
U.  S.  Engineers,  Brevet  Major-General  U. 
S.   Army.    Nine  plates,  views,  etc.    8vo, 
cloth,  2  50 

GILLMORE.  A  PRACTICAL  TREATISE  ON  THE 
CONSTRUCTION  OF  ROADS,  STREETS,  AND 
PAVEMENTS.  By  Q.  A.  Gillmore,  Lt.-Col. 
U.  S.  Engineers,  Brevet  Major-General  U, 
S.  Army.  Seventy  illustrations.  I2mo,  clo.,  200 

GILLMORE.  REPORT  ON  STRENGTH  OF  THE  BUILD- 
ING STONES  IN  THE  UNITED  STATES,  etc. 
'     8vo,  cloth, 1  00 

HOLLEY.  AMERICAN  AND  EUROPEAN  RAILWAY 
PRACTICE,  in  the  Economical  Generation 
of  Steam.  By  Alexander  L.  Holley.  B.  P. 
With  77  lithographed  plates.  Folio,  cloth,  12  00 


D.  VAN  NOSTRAND'S  PUBLICATIONS. 

HAMILTON.  USEFUL  INFORMATION  FOR  RAIL- 
WAY MEN.  Compiled  Ivy  W.  G.  Hamilton, 
Engineer.  Seventh  edition,  revised  and  en- 
larged. 577  pages.  Pocket  form,  morocco, 
gilt, ,  .  $2  00 

STUART.  THE  CIVIL  AND  MILITARY  ENGINEERS 
OF  AMERICA.  By  General  Charles  B. 
Stuart,  Author  of  "Naval  Dry  Docks  of 
the  United  States,"  etc.,  etc.  With  nine 
finely-executed  Portraits  on  steel,  of  emi- 
nent Engineers,  and  illustrated  by  En- 
gravings of  some  of  the  most  important 
and  original  works  constructed  in  Ameri- 
ca. 8vo,  cloth, 5  00 

ERNST.  A  MANUAL  OF  PRACTICAL  MILITARY 
ENGINEERING.  Prepared  for  the  use  of  the 
Cadets  of  the  U.  8.  Military  Academy, 
and  for  Engineer  Troops.  By  Capt.  O.  H. 
Ernst,  Corps  of  Engineoi-s,  Instructor  in 
Practical  Military  Engineering,  U.  S. 
Military  Academy.  193  wood-cuts  and  3 
lithographed  plates.  12mo,  cloth,  .  .  5  00 

SIMMS.  A  TREATISE  ON  THE  PRINCIPLES  AND 
PRACTICE  OF  LEVELLING,  showing  its  ap- 
plication to  purposes  of  Railway  Engineer- 
ing and  the  Construction  of  Roads,  etc. 
By  Frederick  W.  Simms,  C.  E.  From  the 
fifth  London  edition,  revised  and  correct- 
ed, with  the  addition  of  Mr.  Law's  Prac- 
tical Examples  for  Setting-out  Railway 
Curves.  Illustrated  with  three  lithograph- 
ic plates,  and  numerous  wood-cuts.  8vo, 
cloth, 2  50 

JEFFERS.  NAUTICAL  SURVEYING.  By  William 
N.  Jeffers,  Captain  U.  8.  Navy.  Illustrat- 
ed with  9  copperplates,  and  31  wood-cut 
illustrations.  8vo,  cloth,  .  .  .  .  5  00 

THE  PLANE  TABLE.  ITS  USES  IN  TOPOGRAPHI- 
CAL  SURVEYING.  From  the  papers  of  the 
U.  S.  Coast  Survey.  8vo,  cloth,  .  2  00 


D.  VAN  NOSTRAND'S  PUBLICATIONS. 

A  TEXT-BOOK  ON  SURVEYING,  PROJECTIONS, 
AND  PORTABLE  INSTRUMENTS,  for  the  use 
of  the  Cadet  Midshipmen,  at  the  U.  S. 
Naval  Academy.  9  lithographed  plates, 
and  .several  wood-cuts.  8vo,  cloth,  .  .  $2  00 

CHAUVENET.  NEW  METHOD  OF  CORRECTING 
LUNAR  DISTANCES.  By  Wm.  Chauvenet, 
LL.D.  8vo,  cloth, 2  00 

BURT.  KEY  TO  THE  SOLAR  COMPASS,  and  Sur- 
veyor's Companion;  comprising  all  the 
Rules  necessary  for  use  in  the  Field.  By 
W.  A.  Burt,  U.  S.  Deputy  Surveyor.  Sec- 
ond edition.  Pocket-book  form,  tuck,  .  2  50 

HOWARD,   EARTHWORK  MENSURATION  ON  THE 

BASIS    OF     THE      PRISMOlDAL     FORMULAE. 

Containing  simple  and  labor-saving  meth- 
od of  obtaining  Prisinoidal  Contents  direct- 
ly from  End  Areas.  Illustrated  by  Exam- 
ples, and  accompanied  by  Plain  Rules  for 
practical  uses.  By  Con  way  R.  Howard, 
Civil  Engineer,  Richmond,  Va.  Illustrat- 
ed. 8vo,  cloth, 1  50 

MORRIS.  EASY  RULES  FOR  THE  MEASUREMENT 
OF  EARTHWORKS,  by  means  of  the  Pr.is- 
inoidal  Formulae.  By  El  wood  Morris, 
Civil  Engineer.  78  illustrations.  8vo,  cloth,  1  50 

CLEVENGER.  A  TREATISE  ON  THE  METHOD  OF 
GOVERNMENT  SURVEYING,  as  prescribed 
by  the  U.  S.  Congress  and  Commissioner  of 
the  General  Land  Office.  With  complete 
Mathematical,  Astronomical,  and  Practi- 
cal Instructions  for  the  use  of  the  U.  S. 
Surveyors  in  the  Field.  By  S.  V.  Cleven- 
ger,  U.  S.  Deputy  Surveyor.  Illustrated. 
Pocket  form,  morocco,  gilt,  .  .  .  250 

HEWSON.  PRINCIPLES  AND  PRACTICE  OP  EM- 
BANKING LANDS  from  River  Floods,  as 
applied  to  the  Levees  of  the  Mississipi. 
By  William  Hewson,  Civil  Engineer.  «vo, 

cloth, .      2  00 

12 


D.  VAN  NOSTRAND'S  PUBLICATIONS. 

MINIFIE.  A  TEXT-BOOK  OF  GEOMETRICAL 
DRAWING,  for  the  use  of  Mechanics  and 
Schools.  With  Illustrations  for  Drawing 
Plans,  Elevations  of  Buildings  and  Ma- 
chinery. With  over  200  diagrams  on  steel. 
By  William  Minifie,  Architect.  Ninth  edi- 
tion. Royal  8vo,  cloth, $4  00 

MINIFIE.  GEOMETRICAL  DRAWING.  Abridged 
from  the  octavo  edition,  for  the  use  of 
Schools.  lUustrated  with  48  steel  plates. 
New  edition,  enlarged.  I2rno,  cloth,  2  00 

FREE  HAND  DRAWING.  A  GUIDE  TO  ORNAMEN- 
TAL, Figure,  and  Landscape  Drawing.  By 
an  Art  Student.  Profusely  illustrated. 
I8ino,  boards, 50 

AXON.  THE  MECHANIC'S  FRIEND.  A  Collec- 
tion of  Receipts  and  Practical  Suggestions, 
relating  to  Aquaria— Bronzing— Cenients 
—Drawing — Dyes— Electricity— Gilding — 
Glass-working— Glues  —  Horology  —  Lac- 
quers—Locomotives —Magnetism  —  Metal- 
working  —  Modelling  —  Photography— Py- 
rotechiiy— Railways— S9lders— Steam  -  En- 
gine—Telegraphy—Taxidermy—Varnishes 
— Waterproofing-and  Miscellaneous  Tools, 
Instruments,  Machines,  and  Processes 
connected  with  the  Chemical  and  Mechan- 
ical Arts.  By  William  E.  Axon,  M.R.S.L. 
12ino,  clotu.  300  illustrations,  .  .  .  1  50 

HARRISON.  MECHANICS'  TOOL  BOOK,  with 
Practical  Rules  and  Suggestions,  for  the 
use  of  Machinists,  Iron  Workers,  and  oth- 
ers. By  W.  B.  Harrison.  44=  illustrations. 
I2nio,  cloth 1  50 

JOYNSON.  THE  MECHANIC'S  AND  STUDENT'S 
GUIDE  in  the  designing  and  Construction 
of  General  Machine  Gearing.  Edited  by 
Francis  H.  Joynson.  With  18  folded 
plates.  8vo,  cloth  .  .  2  00 

13 


D.  VAN  NOSTRAND'S  PUBLICATIONS. 

RANDALL.  QUARTZ  OPERATOR'S  HAND-BOOK. 
By  P.  M.  Randall.  New  Edition.  Revised 
and  Enlarged.  Fully  illustrated.  12mo, 
cloth, .  .  $2  00 

SILVERSMITH.  A  PRACTICAL  HAND-BOOK  FOR 
MINERS,  METALLURGISTS,  and  Assayers. 
By  Julius  Silversmith.  Fourth  Edition. 
Illustrated.  12mo,  cloth,  .  .  3  00 

BARNES.  SUBMARINE  WARFARE,  DEFENSIVE 
AND  OFFENSIVE.  Descriptions  of  the  va- 
rious forms  of  Torpedoes,  Submarine  Bat- 
teries and  Torpedo  Boats  actually  used  in 
War.  Methods  of  Ignition  by  Machinery. 
Contact  Fuzes,  and  Electricity,  and  a  full 
account  of  experiments  made  to  deter- 
mine the  Explosive  Force  of  Gunpowder 
under  Water.  Also  a  discussion  of  the  Of- 
fensive Torpedo  system;  its  effect  upon 
Iron-clad  Ship  systems,  and  influence  upon 
future  Naval  Wars.  By  Lieut.-Com.  John 
S.  Barnes,  U.  S.  N.  With  20  lithographic 
plates  and  many  wood-cuts.  8vo,  cloth,  5  00 

FOSTER.  SUBMARINE  BLASTING,  in  Boston 
Harbor,  Mass.  Removal  of  Tower 
and  Corwin  Rocks.  By  John  G.  Foster, 
U.  8.  Eng.  and  Bvt.  Major  General  U.  S. 
Army.  With  seven  Plates.  4to,  cloth,  3  50 

MOWBRAY.  TRI-NITRO-GLYCERINE,  as  ap- 
plied in  the  Hoosac  Tunnel,  and  to  Sub- 
marine Blasting,  Torpedoes,  Quarrying, 
etc.  Illustrated.  8vo,  cloth,  ...  3  00 

WILLIAMSON.    ON  THE  USE  OF  THE  BAROME- 
TER ON  SURVEYS  AND  RECONNAISSANCES. 
Part  I.-Meteorology  in  its  Connection  with 
Hypsometry.    Part  II.— Barometric  Hyp- 
sometry.    ByR.  S.  Williamson,  Bvt.  Lt.- 
Col.  U.S.A.,  Major  Corps    of  Engineers. 
With  illustrative  tables  and  engravings. 
4to,  cloth,    ........    15  00 

14 


D.  VAN  NOSTRAND'S  PUBLICATIONS. 

WILLIAMSON.  PRACTICAL  TABLES  IN  METE 
OKOLOGY  AND  HYP8OMETKY,  in  connection 
with  the  use  of  the  Barometer  By  Col.  R. 
8.  Williamson,  U.  S.  A.  4to,  flexible  cloth,  $2  50 

BUTLER.  PROJECTILES  AND  RIFLED  CANNON 
A  Critical  Discussion  of  the  Principal  Sys 
terns  of  Rifling  and  Projectiles,  with  Prac- 
tical Suggestions  for  their  Improvement. 
By  Oapt.  John  S.  Butler,  Ordnance  Corps, 
U-.  S.  A.  36  Plates.  4to,  cloth,  .  .  7  50 

BENET.  ELECTRO-BALLISTIC  MACHINES,  and 
the  Schultz  Chronoscope.  By  Lt.-Col  S. 
V  Benet,  Chief  of  Ordnance  U.  S.  A. 
Second  edition,  illustrated.  4to,  cloth,  .  3  00 

MICHAELIS.  THE  LE  BOULENGE  CHRONO- 
GRAPH. With  three  lithographed  folding 
plates  of  illustrations.  By  Bvt.  Captian 
O.  E.  Michaelis,  Ordnance  Corpse,  U.  S.  A. 
4to,  cloth,  .  .  .  ...  3  00 

NUGENT.  TTEATISE  ON  OPTICS  ;  or  Light  and 
Sight,  theoretically  and  practically  treat- 
ed ;  with  the  application  to  Fine  Art  and 
Industrial  Pursuits.  By  E.  Nugent.  With 
103  illustrations.  12mo,  cloth,  .  .  1  50 

PEIRCE.  SYSTEM  OF  ANALYTIC  MECHANICS.  By 
Benjamin  Peirce,  Professor  of  Astronomy 
and  Mathematics  in  Harvard  University. 
4to<  cloth,  10  00 

CRAIG-  WEIGHTS  AND  MEASURES.  An  Account 
of  the  Decimal  System,  with  Tables  of  Con- 
version for  Commercial  and  Scientific 
Uses.  By  B.  P.  Craig,  M.  D.  Square  32mo, 
linip  cloth,  .......  50 

ALEXANDER.  UNIVERSAL  DICTIONARY  OF 
WEIGHTS  AND  MEASURES,  Ancient  and 
Modern,  reduced  to  the  standards  of  the 
United  States  of  America.  By  J.  H.  Alex- 
ander. New  edition.  8vo,  cloth,  .  .  3  50 
ID 


D.  VAN  NOSTRAND'S  PUBLICATIONS. 

ELLIOT.  EUROPEAN  LIGHT-HOUSE  SYSTEMS. 
Being  a  Report  of  a  Tour  of  Inspection 
made  in  1873.  By  Major  George  H.  Elliot, 
U.  S.  Engineers.  51  engravings  and  21 
wood-cuts.  8vo,  cloth, $5  00 

SWEET.  SPECIAL  REPORT  ON  COAL.  ByS.  H. 

Sweet.  With  Maps.  8vo,  cloth,  .  .  3  00 

COLBURN.    GAS  WORKS  OF  LONDON.  ByZerah 

Colburn.    12mo,  boards,          .       ...         60 

WALKER.  NOTES  ON  SCREW  PROPULSION,  its 
Rise  and  History.  By  Capt.  W.  H.  Walker, 
U.S. Navy.  8vo,  cloth,  ....  75 

POOR.  METHOD  OF  PREPARING  THE  LINES  AND 
DRAUGHTING  VESSELS  PROPELLED  BY  SAIL 
OR  STEAM,  including  a  Chapter  on  Laying- 
off  on  the  Mould-loft  Floor.  By  Samuel 
M.  Pook,  Naval  Constructor.  Illustrated. 
8vo,  cloth.  5  00 

SAELTZER.  TREATISE  ON  ACOUSTICS  in  connec- 
tion with  Ventilation.  By  Alexander 
Saeltzer.  12mo,  cloth, 2  00 

EASLIE  A  HAND-BOOK  FOR  THE  USE  OF  CON- 
TACTORS, Builders,  Architects,  Engineers, 
Timber  Merchants,  etc.,  with  information 
for  drawing  up  Designs  and  Estimates. 
250  illustrations.  8vo,  cloth,  .  .  .  1  50 

SCHUMANN.  A  MANUAL  OF  HEATING  AND  VEN- 
TILATION IN  ITS  PRACTICAL  APPLICATION 
for  the  use  of  Engineers  and  Architects, 
embracing  a  series  of  Tables  and  Formulae 
for  dimensions  of  heating,  flow  and  return 
Pipes  for  steam  and  hot  water  boilers,  flues, 
etc .  etn  By  F  Schumann,  V.  E.,  U.  S. 
Treasury  Department  12mo.  Illustrated, 
In  vress 

TONER.  DICTIONARY  OF  ELEVATIONS  AND 
CLIMATIC  REGISTER  OF  THE  UNITED  STATES. 
By  J.  M.  Toner,  M,  D.  8vo.  Paper,  $3.00; 
cloth.  ...  .  375 

16 


D.  VAN  NOSTRAND'S  PUBLICATIONS. 

WANKLYN.  MILK  ANALYSIS.  A.  Practical 
Treatise  on  tlio  Examination  of  Milk,  and 
its  Derivatives,  Cream,  Butter,  and 
Cheese.  By  J.  Alfred  Wanklyn,  M.R.C. 
S.  12rno,  cloth,  .  .  .  .  $1  00 

RICE  &  JOHNSON.  ON  A  NEW  METHOD  OF  OB- 
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WEISBACH.  MECHANICS  OF  ENGINEERING,  APPLIED 
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By  Albert  W.  Stahl. 

XXIX.  INJECTORS  ;  their  Theory  and  Use.     Trans- 
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XXX.  TERRESTRIAL  MAGNETISM  AND  THE  MAGNETISM 
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XXXI.  THE   SANITARY    CONDITION  OF  DWELLING 
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No.  40.— TRANSMISSION   OF  POWER   BY  COMPRESSED 

AIR.    B y  Robert  Zahner,  M.  E.    Illustrated. 
No.  41.— STRENGTH  OF  MATERIALS.    By  William  Kent. 
,}0>  42.— VOUSSOIR  ARCHES,  applied  to  Stone  Bridges,  Tun- 
nels, Culverts  and  Domes.    By  Prof.  Wm.  Cain. 
43.— WAVE  AND  VORTEX  MOTION.    By  Dr.  Thomas 

Craig,  of  Johns  Hopkins  University. 
44.— TURBINE  WHEELS.    By  Prof.  W.  P.  Trowbridge. 
~*s»**/45.—  THERMODYNAMICS.     By  Prof.  H.  T.  Eddy. 
35.  46.— ICE-MAKING  MACHINES.  From  the  French  of  M. 

Le  Doux.    Illustrated. 
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Articulated  Links.    By  J.  D.  C.  DeRoos. 
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and  Arrangements.    By  Prof.  W.  H.  Corfield. 
No.  51.— THE    TELESCOPE:     Its    Construe' 

Thomas  Nolan 
No.  52.— IMAGINARY  QUANTITIES:  Translated  1 

French  of  M.  Argand.     By  Prof.  "     " 
io.  53.— INDUCTION  COILS:  How  Made  a 
No.  54.— KINEMATICS  OF  MACHINERY. 

nedy.  With  an  introduction  by  ] 
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WORK.  By  Ben  j.  Baker,  M.  Inst. 
No.  57.— INCANDESCENT  ELECTRIC  LIGF' 

Th.  Du  Moncel  and  Wm.  Henry  T 
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Fairley,  M.  E.,  F.  S.  S. 
No.  59.— RAILROAD    ECONOMICS; 

ments.    By  S.  W.  Robins 
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Detecting  Iir     *\y 
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Dugald  </ 
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THE   UNIVERSITY   S] 


I.— ON  THE  PHYSICAL  BASIS  Ol 
Prof.  T.  ]  .  HUXLEY,  LL.D.  F.K.S. 
t'on  by  a  Professor  in  Yale  College. 
1'ap.' -;:  Covers.     Price  25  cents. 

II.— THE    CORRELATION    OF 
PHYSICAL  FORCES.    By  Prof .  GEORQ! 
M.D.,  of  Yale  College.  36  pp.  Paper  Cove\ 

III.— AS  REGARDS  PROTOPLASM 
to    Prof.    Huxley's   Physical   Basis  of 
HUTCHISON  STIRLING,  F.R.C.S.  pp.  72. 

iv.— ON  THE  HYPOTHESIS' OF  E 

Physical  and    Metaphysical.    By  Prof 
COPE,     12mo.,  72  pp.     Paper  Covers.     Prl 

V.— SCIENTIFIC   ADDRESSES:— 1. j 
thods  and  Tendencies  of  Physical  Invest?  g\ 
Haze  and  Dust.    3.   On  the  Scientific  Use 
nation.    By  Prof.  JOHN  TYNDALL,  F.R.J 
pp.  Paper  Covers.  Price  25  cents.    Flex.  < 

NO.  VI.— NATURAL  SELECTION  , 
TO  MAN.  By  ALFRED  RUSSELL  WAT 
pamphlet  treats  (1)  of  the  Development 
Races  under  the  law  of  selection ;  (2 )  the  1' 
u  ral  Selecti  on  as  applied  to  man .  54  pp. 

NO.  VII.- SPECTRUM  ANALYSIS.  I 
tures  by  Profs.  Rbscoe,  Huggins,  and  Loclj 
ly  illustrated.  88  pp.  Paper  Covers. 

NO.  VIII.— THE   SUN.     A  sketch  of 
state  of  scientific  opinion  as  regards  this  1 
account  of  the  most  recent  discoveries  and! 
observation.     By  Prof.  C.  A.  YOUNG, 
mouth  College.     58  pp.     Paper  Covers. 

NO.  IX.- THE  EARTH  A  GREAT  I 
A.  M.  MAYER,  Ph.D.,  of  Stevens  Institutl 
profoundly  interesting  lecture  on  the  subje 
retism.     72  pp.     Papev  Covers.    Price  25  ( 
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NO.  ;X— MYSTERIES   OF    THE   Vo 
EAR.     By  Prof.  O.  N.  ROOD,  Colombia  C(l 
York.     One  of  the  most  interesting  lecture 
ever  delivered.     Original  discoveries,  briiliaj 
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